Revert "TestExpectations: do not skip document-user-activation.html as the test seems to pass."

This reverts commit 63f4ae00.

Reason for revert: Still fails with leak detector on Linux Trusty Leak.

Original change's description:
> TestExpectations: do not skip document-user-activation.html as the test seems to pass.
> 
> Tested locally and everything is fine.
> 
> Bug: 733494
> Change-Id: I23f3cde42b14d2461fc94a391c6427d5c2aa9e1d
> Reviewed-on: https://chromium-review.googlesource.com/c/1263569
> Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
> Reviewed-by: Becca Hughes <beccahughes@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#610670}

TBR=mlamouri@chromium.org,beccahughes@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 733494
Change-Id: I509b798f79e64b8fb67be392d17a91834fd9c05a
Reviewed-on: https://chromium-review.googlesource.com/c/1350184
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610807}

third_party/blink/web_tests/TestExpectations

@@ -2639,6 +2639,8 @@ crbug.com/483653 accessibility/scroll-containers.html [ Skip ]
 crbug.com/491764 http/tests/devtools/service-workers/user-agent-override.js [ Pass Timeout ]
 
 # Fails with leak detector.
+crbug.com/733494 [ Linux ] media/autoplay/document-user-activation.html [ Skip ]
+crbug.com/733494 [ Linux ] virtual/video-surface-layer/media/autoplay/document-user-activation.html [ Skip ]
 crbug.com/769885 [ Linux ] virtual/android/fullscreen/full-screen-frameset.html [ Skip ]