R1:8d6488f29071

Fix a typo in `bin/repository help update`

Summary: Fixes T10741. The workflow is `refs`, not `ref`.

Test Plan: o.O

Reviewers: chad, cspeckmim

Reviewed By: cspeckmim

Maniphest Tasks: T10741

Differential Revision: https://secure.phabricator.com/D15652