Remove no longer needed WebRTC runtime preferences
<rdar://problem/132000721>
Pull request: https://github.com/WebKit/WebKit/pull/30955
Committed 281124@main (8e0531623ae7): <https://commits.webkit.org/281124@main> Reviewed commits have been landed. Closing PR #30955 and removing active labels.
Re-opened since this is blocked by bug 276907