Otherwise if update_reviewers needs to modify the commit message it won't
show in gerrit.

Bug:

Change-Id: Id81db48b7d15bd17cb924d1d046b31f2c48defa7
Reviewed-on: https://chromium-review.googlesource.com/482062
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>