Minor cleanup of linter testing code.

Summary:
Just some minor cleaning up, including:

• Removing old annotations for Diviner.
• Renaming some lint-test files so that the directory name bears a closer resemblance to that of the linter.
• Remove some useless return statements.

Test Plan: arc unit.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9096