Revert "Disabled external/wpt/editing/run flaky tests"

This reverts commit 75355920.

Reason for revert: The tests themselves are good. The culprit
breaking the test framework has been reverted in
a5c17494

Original change's description:
> Disabled external/wpt/editing/run flaky tests
> 
> TBR=xiaochengh@chromium.org
> 
> Bug: 1097000
> Change-Id: I94edbeb778bf35ea18a18412262ef57e4dfbabdf
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2252145
> Reviewed-by: Andy Paicu <andypaicu@chromium.org>
> Commit-Queue: Andy Paicu <andypaicu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#780261}

TBR=xiaochengh@chromium.org,andypaicu@chromium.org

Change-Id: I80b2b64d5379ce8973e5ce26f8a030c2d496355b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1097000
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2254717Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780393}

third_party/blink/web_tests/TestExpectations

@@ -1622,6 +1622,8 @@ crbug.com/490511 external/wpt/html/rendering/non-replaced-elements/the-hr-elemen
 crbug.com/490511 external/wpt/html/rendering/non-replaced-elements/the-hr-element-0/width.html [ Failure ]
 crbug.com/692560 external/wpt/html/semantics/document-metadata/styling/LinkStyle.html [ Failure Pass ]
 
+crbug.com/860211 [ Mac ] external/wpt/editing/run/delete.html [ Failure ]
+
 crbug.com/821455 editing/pasteboard/drag-files-to-editable-element.html [ Failure ]
 
 crbug.com/688613 external/wpt/mediacapture-streams/MediaStreamTrack-MediaElement-disabled-audio-is-silence.https.html [ Skip ]
@@ -6825,6 +6827,3 @@ crbug.com/1097005 http/tests/devtools/console/console-search.js [ Pass Failure C
 
 crbug.com/1093445 http/tests/loading/pdf-commit-load-callbacks.html [ Pass Failure ]
 crbug.com/1093497 http/tests/history/client-redirect-after-push-state.html [ Pass Failure ]
-
-crbug.com/1097000 external/wpt/editing/run/forwarddelete.html [ Pass Failure ]
-crbug.com/1097000 external/wpt/editing/run/delete.html [ Pass Failure ]