Resync html/browsers/browsing-the-web/navigating-across-documents/replace-before-load WPT from upstream.
Pull request: https://github.com/WebKit/WebKit/pull/13941
Committed 264177@main (67b3e5cb9983): <https://commits.webkit.org/264177@main> Reviewed commits have been landed. Closing PR #13941 and removing active labels.
<rdar://problem/109479162>