[ios/infra] restrict ToTiOS and ToTiOSDevice iOS bots to 10.14

Bots are failing as they sometimes are allocated 10.13 bots when
installing xcode 11.4, which requires OS 10.14. Restricting these
to os.MAC_10_14.

Bug: 1087161
Change-Id: If7b2937fc3bbd3a67f43f07f51e493b395426c03
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225232
Auto-Submit: Jeff Yoon <jeffyoon@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773762}

infra/config/generated/cr-buildbucket.cfg

@@ -7243,7 +7243,7 @@ buckets: <
       swarming_tags: "vpython:native-python-wrapper"
       dimensions: "builderless:1"
       dimensions: "cpu:x86-64"
-      dimensions: "os:Mac"
+      dimensions: "os:Mac-10.14"
       dimensions: "pool:luci.chromium.ci"
       dimensions: "ssd:1"
       recipe: <
@@ -7278,7 +7278,7 @@ buckets: <
       swarming_tags: "vpython:native-python-wrapper"
       dimensions: "builderless:1"
       dimensions: "cpu:x86-64"
-      dimensions: "os:Mac"
+      dimensions: "os:Mac-10.14"
       dimensions: "pool:luci.chromium.ci"
       dimensions: "ssd:1"
       recipe: <

infra/config/subprojects/chromium/master-only/ci.star

@@ -789,7 +789,7 @@ ci.clang_builder(
         short_name = 'sim',
     ),
     cores = None,
-    os = os.MAC_ANY,
+    os = os.MAC_10_14,
     properties = {
         'xcode_build_version': '11c29'
     },
@@ -804,7 +804,7 @@ ci.clang_builder(
         short_name = 'dev',
     ),
     cores = None,
-    os = os.MAC_ANY,
+    os = os.MAC_10_14,
     properties = {
         'xcode_build_version': '11c29'
     },