Stop Phriction handling it's own Subscribers

Summary: Stop Phriction displaying subscribers twice.

Test Plan:
Add Subscriber, remove subscriber, make sure I see only one subscribers list.

Fixes T3534

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T3534

Differential Revision: https://secure.phabricator.com/D6457