Worklet: Use <meta name="timeout"> instead of SlowTests annotations for slow WPTs

<meta name="timeout"> is prefereable for WPTs:
https://web-platform-tests.org/writing-tests/testharness-api.html#harness-timeout

Bug: 912240
Change-Id: I3c4a9acb1fb070c34d10f59ff9d3fd3d2bd11afb
Reviewed-on: https://chromium-review.googlesource.com/c/1366469
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614626}
3 files changed