Legalpad - fix requires signature transaction from always being saved

Summary: Fixes T7295. Humbling debugging experience but I got it.

Test Plan: saved a legalpad doc without edits over and over and saw no "requires signature" transaction. toggled "requires signature", saved, and saw the transaction.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7295

Differential Revision: https://secure.phabricator.com/D11785