Remove overbearing policy checks in Phame

Summary:
Fixes T11584. This controller does unnecessary CAN_EDIT policy checks.

These checks are enforced by EditEngine, and you can make certain types of edits (including comments) even without full-blown edit permission.

Test Plan:

• Commented as a user without edit permission.
• Tried to edit as a user without edit permission, was rebuffed with a policy dialog.
• Edited as a user with edit permission.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11584

Differential Revision: https://secure.phabricator.com/D16493