sheriff: Update TestExpectations for expected css scroll diff flake

Marking external/wpt/css/css-scroll-snap/scroll-margin.html as flaky.
This was previously disabled for prefix virtual/threaded, but because
of a wpt change, we expect the test to flake for all variants.

Bug: 964239
Change-Id: Iee686a55ff9142a81a495ee211b65cbb5a0aa508
Reviewed-by: Madeleine Barowsky <>
Commit-Queue: Madeleine Barowsky <>
Cr-Commit-Position: refs/heads/master@{#661359}
1 file changed