PhabricatorEmailPreferencesSettingsPanel::getAllEditorsWithTags() queries for all classes extending PhabricatorApplicationTransactionEditor and having getMailTagsMap() to then pull their editor application class. Thus return the correct editor application class.
Followup to rP821708414e.
grep -r "('PhabricatorApplicationTransactionEditor'" . shows only a single result in the Phorge codebase (this PhutilClassMapQuery->setAncestorClass('PhabricatorApplicationTransactionEditor') call) so I assume there will be no unwanted side effects.
Closes T16002