Promote the cros_vm_sanity_test from experimental on the cros VM CQ bot.

It appears that the timeout+retries I added in CL:1102121 are
successfully making the test more stable. See the following tests that
froze, were caught+retried, and passed:
https://chromium-swarm.appspot.com/task?id=3e2d8a94a80e7a10
https://chromium-swarm.appspot.com/task?id=3e2d2fdf269c5910

Bug: 840967
Change-Id: Ie4f02862201965e27af437c88e9a5e4ec0feccbf
Reviewed-on: https://chromium-review.googlesource.com/1105314Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568289}

testing/buildbot/chromium.chromiumos.json

@@ -59,7 +59,6 @@
         "test": "cc_unittests"
       },
       {
-        "experiment_percentage": 100,
         "swarming": {
           "can_use_on_swarming_builders": true,
           "dimension_sets": [

testing/buildbot/test_suites.pyl

@@ -349,9 +349,7 @@
     'cacheinvalidation_unittests': {},
     'capture_unittests': {},
     'cc_unittests': {},
-    'cros_vm_sanity_test': {
-      'experiment_percentage': 100,
-    },
+    'cros_vm_sanity_test': {},
     'crypto_unittests': {},
     'display_unittests': {},
     'google_apis_unittests': {},