Don't show "edit" links in Differential for now

Summary: Ref T2222. These don't work yet. We just have to copy a couple fields, but let's sort that out later since this is purely a new feature.

Test Plan: Looked at a revision, no edit links.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8222