R1:a39852ae1b4a

Remove pointless requireCapabilities() method from PhabricatorProjectColumnTransactionEditor

Summary:
Depends on D19581. Ref T13164. This method has no effect:

- You must always have CAN_EDIT to reach an Editor in the first place.
- Per previous change, I'm going to restructure this so transactions explicitly check CAN_EDIT by default anyway.

Test Plan: Tried to edit and hide a project column as a user without permission, hit global permission checks long before reaching this method.

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