Fix a broken migration

Summary: Ref T7604. This migration doesn't actually work because it is in the wrong directory.

Test Plan: Ran ./bin/storage upgrade and saw the migration applied.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7604

Differential Revision: https://secure.phabricator.com/D13014