Remove Oreo Playstore dimension

Removes the Playstore version dimension from the AR tests running on
Oreo. The Playstore version on the devices has changed, causing there to
be no matching devices for testing, and the current version seems to
work fine for the tests.

Bug: 1168739
Change-Id: Id765b91a46b59789782d6e00593f49f0945c5ac7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2645348
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846364}

testing/buildbot/chromium.android.json

@@ -17464,7 +17464,6 @@
             {
               "device_os": "OPR3.170623.008",
               "device_os_type": "userdebug",
-              "device_playstore_version": "12.8.23-all",
               "device_type": "marlin",
               "os": "Android"
             }

testing/buildbot/test_suite_exceptions.pyl

@@ -1726,7 +1726,6 @@
           'dimension_sets': [
             {
               'device_os': 'OPR3.170623.008',
-              'device_playstore_version': '12.8.23-all',
               'device_type': 'marlin',
               'os': 'Android',
             },