Update multi_repo_trybots documentation.

Some Chromium build bots are not configured with a current git user.name
and user.email. As a result cherry-pick will fail to commit. Add a fake
committer name and email to the cherry-pick command line to avoid this.

Change-Id: If8020965d1b7d54c1651f704bfb04deaaaa64073
Reviewed-on: https://skia-review.googlesource.com/130601
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed