chromeos: Disable security.SELinuxFilesARC in chrome_all_tast_tests.

R=achuith

Bug: 968155, 947531
Change-Id: I97d2efaf7a04c4c31994929f987baa919a732dc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635197
Auto-Submit: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664329}

chromeos/BUILD.gn

@@ -233,6 +233,7 @@ if (is_cros_chrome_sdk) {
   tast_test("chrome_all_tast_tests") {
     # To disable a specific test, add it the following list.
     tast_disabled_tests = [
+      "security.SELinuxFilesARC",  # crbug.com/968155
       "ui.MashLogin",
       "ui.SingleProcessMashLogin",
     ]