Silence deprecation warnings for _handleKeyUIEvent to fix the build with the latest iOS SDK.
<rdar://problem/100620111>
Pull request: https://github.com/WebKit/WebKit/pull/4861
Committed 255027@main (ef452225e3b1): <https://commits.webkit.org/255027@main> Reviewed commits have been landed. Closing PR #4861 and removing active labels.