Allow public on list of subscribers
Summary: Fixes T7317, allows public to be set on this list controller.
Test Plan: Tested a list of subscribers on a logged in and logged out Diff.
Reviewers: btrahan, epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T7317
Differential Revision: https://secure.phabricator.com/D11801