Make sure isLatin1() is a no-op for LChar characters.
<rdar://problem/107666559>
Pull request: https://github.com/WebKit/WebKit/pull/12413
Committed 262627@main (b15ce8abf9da): <https://commits.webkit.org/262627@main> Reviewed commits have been landed. Closing PR #12413 and removing active labels.