Disable flaky external/wpt/css/css-images/image-set/image-set-parsing.html

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1166602
Change-Id: I319bd450947624388df6e3c2539edc0bfdca59d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628292Reviewed-by: Andy Paicu <andypaicu@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Auto-Submit: Andy Paicu <andypaicu@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843487}

third_party/blink/web_tests/TestExpectations

@@ -5847,6 +5847,7 @@ crbug.com/1164459 [ Mac10.15 ] external/wpt/preload/download-resources.html [ Pa
 
 # Sheriff 2021-01-14
 crbug.com/1166540 [ Mac ] ietestcenter/css3/bordersbackgrounds/background-attachment-local-scrolling.htm [ Pass Failure ]
+crbug.com/1166602 external/wpt/css/css-images/image-set/image-set-parsing.html [ Pass Failure ]
 
 # CSS spelling and grammar features (issue 1163437)
 crbug.com/1147859 external/wpt/css/css-pseudo/highlight-painting-order.html [ Failure ]