Allow public access to the project edit/history page

Summary: Fixes T6807. This page shows edit history and has edit options, but is not an edit interface itself per se. Allowing public access is consistent with other interfaces/applications.

Test Plan: Viewed a public project's history page as a public user.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T6807

Differential Revision: https://secure.phabricator.com/D11039