System Services: Replace uses of "master" in code search links with "HEAD"

This will still work after git "master" branch is renamed to "main",
and makes inclusive language dashboards easier to interpret right now.

R=khorimoto@chromium.org

Bug: none
Test: none
Change-Id: I7c4ab86938bf18cf6fb29673ba177b98a48efbcf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2518831Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Miriam Zimmerman <mutexlox@chromium.org>
Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823788}

device/bluetooth/bluez/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Network>Bluetooth"

device/bluetooth/chromeos/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Network>Bluetooth"

extensions/browser/api/feedback_private/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "Platform>Apps>Feedback"

ui/events/keycodes/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "IO>Keyboard"

ui/webui/resources/cr_components/chromeos/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Settings"

ui/webui/resources/cr_components/chromeos/multidevice_setup/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Multidevice"

ui/webui/resources/cr_components/chromeos/network/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Network>General"

ui/webui/resources/cr_components/chromeos/quick_unlock/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Settings"

ui/webui/resources/cr_elements/chromeos/DIR_METADATA

 # Metadata information for this directory.
 #
 # For more information on DIR_METADATA files, see:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/README.md
 #
 # For the schema of this file, see Metadata message:
-#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+#   https://source.chromium.org/chromium/infra/infra/+/HEAD:go/src/infra/tools/dirmd/proto/dir_metadata.proto
 
 monorail {
   component: "OS>Systems>Settings"