Simplify treeScope handling logic in CSSStyleSheetObservableArray.
Pull request: https://github.com/WebKit/WebKit/pull/11565
Committed 261733@main (5411d5fd0a7a): <https://commits.webkit.org/261733@main> Reviewed commits have been landed. Closing PR #11565 and removing active labels.
<rdar://problem/106790890>