Clean up logged out prompt on TransactionComments

Summary: We were getting a weird double box here, missed it my first pass

Test Plan: Review logged in Maniphest and Paste, as well as logged out versions. Test Login flow.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7716