Disable AdaptiveScreenBrightnessManagerTest.MultipleBrowsersNoneActive

Disable the test by sheriff because it's flaky.

Bug: 938289
Change-Id: I9e9bd5820444562e5485c0a1b445960278cc97dd
Tbr: derat@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504115
Reviewed-by: Owen Min <zmin@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637789}
1 file changed