When purging drafts after a transaction edit, purge all drafts

Summary: Fixes T13071. See that task for discusison. I think this <= version constraint is needless in normal cases (it should match everything in the table anyway), and slightly harmful in bizarre cases where a draft somehow gets a much larger ID than it should have.

Test Plan:

• Gave a draft an unreasonably large ID.
• Pre-patch, observed: submitting comments on the draft's object does not clear the draft.
• Post-patch: submitting comments on the draft's object now clears the draft correctly.
• Also added comments/actions, reloaded pages, saw drafts stick properly.

Maniphest Tasks: T13071

Differential Revision: https://secure.phabricator.com/D19060