Remove legacy support for 'phd repository-launch' and 'phd repository-launch-readonly'

Summary: These have been marked as deprecated since May 2012. Clean them up.

Test Plan: Grepped for repository-launch, phd_load_tracked_repositories: no hits.

Reviewers: btrahan, vrana

Reviewed By: vrana

CC: aran

Maniphest Tasks: T2372

Differential Revision: https://secure.phabricator.com/D4575