Android test exclusions: don't exclude components_background_task_scheduler_junit_tests

These tests do pass on some bots, e.g. [1], and it's not clear why they were
being excluded. If there's a legitimate reason for them not to run on Android,
let's figure it out and get a bug filed.

Sheriffs: if this causes the tests to start failing on Android bots, please
file a bug with information about the error, put the exclusion back and
reference the bug.

Bug: 842698

 [1] https://ci.chromium.org/buildbot/chromium.clang/ToTAndroid/3343

Change-Id: Iee4f0a51ee32cc66d4a56620d181d2f090486041
Reviewed-on: https://chromium-review.googlesource.com/1061235Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559052}

testing/buildbot/chromium.android.json

@@ -2144,6 +2144,9 @@
       {
         "test": "chrome_junit_tests"
       },
+      {
+        "test": "components_background_task_scheduler_junit_tests"
+      },
       {
         "test": "components_gcm_driver_junit_tests"
       },

testing/buildbot/test_suite_exceptions.pyl

@@ -688,19 +688,6 @@
       'ToTLinuxASan',
     ],
   },
-  'components_background_task_scheduler_junit_tests': {
-    'remove_from': [
-      # On chromium.android, unclear why these aren't run on all bots.
-      'KitKat Phone Tester (dbg)',
-      'KitKat Tablet Tester',
-      'Lollipop Phone Tester',
-      'Lollipop Tablet Tester',
-      'Marshmallow 64 bit Tester',
-      'Marshmallow Phone Tester (rel)',
-      'Marshmallow Tablet Tester',
-      'Nougat Phone Tester',
-    ],
-  },
   'components_browsertests': {
     'remove_from': [
       # chromium.chromiumos