Mark removeformat.html as flaky

BUG=813098
TBR=editing-dev

Change-Id: I9005cfc1cf4011ee0b424cb7f06270786115a386
Reviewed-on: https://chromium-review.googlesource.com/924221Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
Commit-Queue: Thiemo Nagel <tnagel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537334}

third_party/WebKit/LayoutTests/TestExpectations

@@ -822,6 +822,8 @@ crbug.com/627706 external/wpt/html/semantics/embedded-content/the-img-element/in
 
 crbug.com/698135 external/wpt/editing/run/delete.html [ Crash Failure Timeout ]
 
+crbug.com/813098 external/wpt/editing/run/removeformat.html [ Timeout Pass ]
+
 crbug.com/688613 external/wpt/mediacapture-streams/MediaStreamTrack-MediaElement-disabled-audio-is-silence.https.html [ Skip ]
 crbug.com/688613 virtual/feature-policy-permissions/external/wpt/mediacapture-streams/MediaStreamTrack-MediaElement-disabled-audio-is-silence.https.html [ Skip ]