Update fast/scrolling/mac/scrollbars tests to use new UIHelper scrollbar state function
<rdar://problem/107389069>
Pull request: https://github.com/WebKit/WebKit/pull/12140
Committed 262561@main (3a9451dba313): <https://commits.webkit.org/262561@main> Reviewed commits have been landed. Closing PR #12140 and removing active labels.