Phortune - require high security sessions for subscription edits

Summary: Ref T7202.

Test Plan: Visited edit subscription page and it worked. Clicked edit link from subscription view page and got to the right place.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7202

Differential Revision: https://secure.phabricator.com/D11803