We should convert UpdatePullRequest to a new-style buildstep so that we can use Twisted's asynchronous request infrastructure.
<rdar://problem/105130791>
Pull request: https://github.com/WebKit/WebKit/pull/9757
Committed 260227@main (a908c00f5705): <https://commits.webkit.org/260227@main> Reviewed commits have been landed. Closing PR #9757 and removing active labels.