Strip tips out of commit messages from arc backout
Fixes T10707. Currently, arc backout creates a commit message which includes questionably-helpful "tips" in the message itself.
Strip these out.
Used arc backout to revert any commit, then git show to see the generated message.
- Before patch: included tips.
- After patch: no tips.
Reviewed By: chad
Maniphest Tasks: T10707
Differential Revision: https://secure.phabricator.com/D15573