Update identifier for WebKit process extensions.
<rdar://problem/123460280>
Pull request: https://github.com/WebKit/WebKit/pull/24967
Committed 275210@main (7301277d5018): <https://commits.webkit.org/275210@main> Reviewed commits have been landed. Closing PR #24967 and removing active labels.
Re-opened since this is blocked by bug 269962