Don't use CommentEditor in lipsum

Summary: Ref T2222. For now, I'm just dropping this rather than updating it since I'll need to come back here later for DifferentialRevisionEditor anyway, and no users rely on this functionality.

Test Plan: Static checks; this isn't user-facing.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8426