Don't require admin privileges to verify email addresses

Summary: Fixes T2821. In D5386 we locked most of this app down, but missed one controller which needs to be accessible by non-admins (this controller should probably be in some other app, like auth, in the long term).

Test Plan: @shanemhansen confirmed this fixed his install

Reviewers: chad, AnhNhan

Reviewed By: chad

CC: shanemhansen, aran

Maniphest Tasks: T2821

Differential Revision: https://secure.phabricator.com/D5422