Convert LeaveComment step to a new-style build step using 'run' instead of 'start'.
<rdar://problem/104750744>
Pull request: https://github.com/WebKit/WebKit/pull/9240
Committed 259594@main (93717e0e29c4): <https://commits.webkit.org/259594@main> Reviewed commits have been landed. Closing PR #9240 and removing active labels.