Policy - convert Drydock query for repository to policy-based query

Summary: Ref T7094. Switch to OmnipotentUser policy-based query since this is usually done offline, etc.

Test Plan: pretty simple code change so I just have my fingers crossed while I am typing this

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7094

Differential Revision: https://secure.phabricator.com/D11655