Remove unused PhabricatorApplicationTransactionCommentView::getStatusID()

Summary: Calls to this private function were removed in https://we.phorge.it/rPeded19a5c6d3e5fa4e0d655bc8271d2a5baa5a34.

Test Plan: Grep the code; run static code analysis.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25787