Remove `SKIP` expectations for Mac tests related to scroll animations.
Remove `SKIP` expectations for Mac tests related to scroll animations.

These layout tests were skipped on Mac since it used to be impossible to enable
scroll animations on a per-test basis in Mac. This was fixed in r376025 so these
tests should be able to run now.

BUG=364614

Review URL: https://codereview.chromium.org/1897973006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#388619}

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