Remove lint message counts from Diffusion repository list

Summary: We should bring these back some day, but they should be denormalized, inside the query, and there should be a better pipeline to build them in the first place. Just get rid of them for now; this essentially impacts only us.

Test Plan: Loaded `/diffusion/`, same page minus lint counts.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, vrana

Differential Revision: https://secure.phabricator.com/D6915