Move telemetry_unittests out of experimental on cros VM CQ bot.

It's been at 100% experimental for a while now and it doesn't appear
to be blowing out our capacity.

Bug: 876494
Change-Id: I90a4fda3350bd96a03244d9b53b0471ce66923a8
Reviewed-on: https://chromium-review.googlesource.com/c/1301971Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603567}

testing/buildbot/chromium.chromiumos.json

@@ -391,7 +391,6 @@
           "--remote=127.0.0.1",
           "--remote-ssh-port=9222"
         ],
-        "experiment_percentage": 100,
         "isolate_name": "telemetry_unittests",
         "name": "telemetry_unittests",
         "swarming": {

testing/buildbot/test_suites.pyl

@@ -479,8 +479,6 @@
           '--remote=127.0.0.1',
           '--remote-ssh-port=9222',
         ],
-        # TODO(crbug.com/876494): Move this out of experimental.
-        'experiment_percentage': 100,
         'swarming': {
           'hard_timeout': 1200,
           'idempotent': False,  # https://crbug.com/549140