Add a "--force" flag to "bin/repository move-paths"

Summary:
Ref T7148. The automated export process runs this via daemon, which can't answer "Y" to this prompt. Let it "--force" instead.

(Some of my test instances didn't have any repositories, which is why I didn't catch this sooner.)

Test Plan: Ran bin/repository move-paths --force ..., saw change applied without a prompt.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7148

Differential Revision: https://secure.phabricator.com/D16426