[Cocoa] Delete dead code after cleaning up HAVE() and USE() macros
<rdar://problem/111198556>
Pull request: https://github.com/WebKit/WebKit/pull/15225
Committed 265448@main (6a90e53bcf69): <https://commits.webkit.org/265448@main> Reviewed commits have been landed. Closing PR #15225 and removing active labels.
Re-opened since this is blocked by bug 258444