Enable external/wpt/workers/opaque-origin.html

There haven't been any crashes or timeouts in a long time, only normal failures:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=%2Fworkers%2Fopaque-origin.html

See https://github.com/web-platform-tests/wpt/issues/11188.

Change-Id: I933124b8c406fd202a7d382350cfe259d6607d79
Reviewed-on: https://chromium-review.googlesource.com/1140053
Commit-Queue: Robert Ma <robertma@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575647}
2 files changed