Lint JSON files with ArcanistJSONLinter.
Summary: After D9628, we can lint JSON files natively.
Test Plan: See D9652.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D9654