Legacy aliases are just parse time aliases, so they should just serialize to their modern counterpart rather than trying to roundtrip.
<rdar://problem/120360545>
Pull request: https://github.com/WebKit/WebKit/pull/22296
Committed 272564@main (b06889b80ece): <https://commits.webkit.org/272564@main> Reviewed commits have been landed. Closing PR #22296 and removing active labels.