Remove Differential "Title" custom field
Summary: Ref T11114. Obsoleted by Modular Transactions + EditEngine + CommitMessageField + we just "hard code" the title of revisions into the page because we're craaazy.
Test Plan:
- Made an edit on stable.
- Viewed the edit on this change, it still had the proper UI strings.
- Edited/created/updated revisions.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T11114
Differential Revision: https://secure.phabricator.com/D17083