Drop custom IPC decoder / encoder for WTF::MachSendRight.
Pull request: https://github.com/WebKit/WebKit/pull/23466
Committed 273876@main (5bf2fff545a7): <https://commits.webkit.org/273876@main> Reviewed commits have been landed. Closing PR #23466 and removing active labels.
<rdar://problem/122058289>