Stop prewarming GPU drivers on newer versions of macOS, since this prevents us from blocking IOKit in the WebContent process.
<rdar://problem/101976270>
Pull request: https://github.com/WebKit/WebKit/pull/6149
Committed 256418@main (9aeed97c81b9): <https://commits.webkit.org/256418@main> Reviewed commits have been landed. Closing PR #6149 and removing active labels.