Bug 1729735 [wpt PR 30400] - Update scroll-animation tests to be independent of scrol...

Bug 1729735 [wpt PR 30400] - Update scroll-animation tests to be independent of scrollbar width, a=testonly

Automatic update from web-platform-tests
Update scroll-animation tests to be independent of scrollbar width

This patch addresses sources of test failures observed when implementing
a polyfill implementation of scroll timelines. Different platforms can
use different scrollbar widths, which leads to some changes in
expectations. By hiding the scrollbars, we have consistency across
platforms and avoid fractional scroll offsets.

Previous expectations may be the source of Mac failures.
Deferring possible re-enabling of Mac tests to a followup CL.

Bug: 1246372
Change-Id: I6b7ad072af495b23e4acf0654a210847de8cb78b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3149090
Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Cr-Commit-Position: refs/heads/main@{#919758}

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wpt-commits: ef3d38ed29fcc2760eaf3af45d9eb8a0845522ff
wpt-pr: 30400