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