Remove patch preview from Phragment version controller

Summary: Patches can exceed the 30 second time out in most PHP installations. This removes the patch preview from the version controller so that users can still see the information (although they may not be able to download the actual patch).

Test Plan: Viewed a version and saw that the patch didn't appear.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7767