build: remove unused references to swarming_client

subprocess42 is not used by test_runner.py anymore.

Bug: 1050466
Change-Id: Ifd064b362d13c778c59cfd3e3d56939f6fe052c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2053750Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741109}

build/chromeos/test_runner.py

@@ -399,7 +399,6 @@ class GTestTest(RemoteTest):
       # //testing/buildbot/filters/.
       re.compile(r'.*testing/(?!buildbot/filters).*'),
       re.compile(r'.*third_party/chromite.*'),
-      re.compile(r'.*tools/swarming_client.*'),
   ]
 
   def __init__(self, args, unknown_args):

build/config/chromeos/rules.gni

@@ -84,9 +84,6 @@ template("generate_runner_script") {
       "//build/cros_cache/chrome-sdk/misc/",
       "//build/cros_cache/chrome-sdk/symlinks/",
 
-      # We use luci-py's subprocess42 to launch test processes.
-      "//tools/swarming_client/utils/",
-
       # The LKGM file controls what version of the VM image to download. Add it
       # as data here so that changes to it will trigger analyze.
       "//chromeos/CHROMEOS_LKGM",