Remove UI warnings about policies being a janky mess

Summary: Ref T603. While policies aren't completely perfect, they are substantially functional to the best of my knowledge -- definitely in good enough shape that we want to hear about issues with them, now.

Test Plan: Edited a task, repository, and project.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7343