R1:cd449254256d

Allow users with no CAN_EDIT permissions to silence projects if they want to

Summary: Humble user cannot silence/mute project if he/she has no CAN_EDIT permissions in it. You can actually leave it but if project is locked - then you're scr*wed.

Test Plan:
1. On a testing phabricator instance created a dummy project
2. Changed that project permissions CAN_EDIT to be by admin only
3. Added poor soul with no CAN_EDIT permissions
4. Logged it in with poor soul
5. Tried to silence the project
6. The Project…