Allow pastes to be destroyed

Summary: Fixes T6186.

Test Plan:

• Used bin/remove destroy Pxxx to destroy a paste.
• Verified file, transactions, etc., were destroyed.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6186

Differential Revision: https://secure.phabricator.com/D10563