Policy - fix error message

Summary: We were saying "Object Restricted Object"; instead say "Restricted Object". Fixes T6104.

Test Plan: made a restricted paste and a restricted task and saw good error messages.

Reviewers: epriestley, chad

Reviewed By: chad

Subscribers: Korvin, epriestley

Maniphest Tasks: T6104

Differential Revision: https://secure.phabricator.com/D10668