To adopt Twisted requests, RemoveLabelsFromPullRequest needs to be a new-style buildbot step.
<rdar://problem/104669946>
Pull request: https://github.com/WebKit/WebKit/pull/9155
Committed 259394@main (7e9c19c3d24d): <https://commits.webkit.org/259394@main> Reviewed commits have been landed. Closing PR #9155 and removing active labels.