Fix Phriction document migration after project magic removal

Summary: See <https://github.com/phacility/phabricator/issues/760>. We removed these methods in D10832 but still need the migration to be able to do project checks.

Test Plan: Ran on a test wiki with `/`, `/projects/` and `/projects/example/`. The first two pages didn't try to use project policies; the third one did.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10836