Change baseURI for Packages to avoid 404

Summary: Without this change, the landing page for the Packages app is https://secure.phabricator.com/packages, which is a 404. There's probably a better way to fix this, but this was the fewest characters.

Test Plan: doitlive

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D21494