R1:2b8116d7ae0a

Fix error cues on "Edit Revision" interface

Summary: The field hints on this interface don't behave correctly. Particularly, when you add yourself as a reviewer you aren't pointed at the issue.

Test Plan: Edited a revision and tried to save invalid changes, including self-reviewership.

Reviewers: moskov, jungejason, tuomaspelkonen, aran

CC:

Differential Revision: 565