GitHubMixin.get_pr_json makes a network request, so it should adopt Twisted's asynchronous request library.
<rdar://problem/107207345>
Pull request: https://github.com/WebKit/WebKit/pull/11954
Committed 262151@main (9a18fa3e56d4): <https://commits.webkit.org/262151@main> Reviewed commits have been landed. Closing PR #11954 and removing active labels.