R1:f9a59c9f4999

Enable "Resign as Reviewer" from Differential Revision View UI

Summary:
Enable "Resign as Reviewer" from Differential Revision View UI

Test Plan:
Look at revision that I am a reviewer on and that I am not.

Reviewed By: epriestley
Reviewers: epriestley
CC: epriestley
Differential Revision: 120