Remove arcconfig settings from ArcanistLinterTestCase
Summary: This doesn't make too much sense anymore as all modern linters are configured via the .arclint file rather than .arcconfig.
Test Plan: grepped to make sure this option isn't used.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D11173