R1:b0bba4d14235

Remove unused methods in PhabricatorEditorExtension

Summary:
The methods `newRequiredTransasctionError()` [sic!] and `newInvalidTransactionError()` are not called anywhere in the codebase. Both are `final protected`, thus remove them.

Incidentally, speedup Diviner generation by at least 0.000000000000000000000001 milliseconds.

Test Plan: Grep the code.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan…