We do not need to worry about zones, nor is the method overridden, so we can replace this method with mutableCopy.
Pull request: https://github.com/WebKit/WebKit/pull/11440
<rdar://problem/106942513>
Committed 262083@main (c0b2221b92ed): <https://commits.webkit.org/262083@main> Reviewed commits have been landed. Closing PR #11440 and removing active labels.