[Cocoa] RemoteAudioDestinationProxy threads are created with too low a priority for realtime audio
<rdar://problem/115513480>
Pull request: https://github.com/WebKit/WebKit/pull/17825
Committed 268047@main (3468951fe890): <https://commits.webkit.org/268047@main> Reviewed commits have been landed. Closing PR #17825 and removing active labels.