Remove "arc lint --cache"

Summary: Ref T12996. This is another half-baked Facebook-specific feature. Clear it out of the way so arc lint can be modernized more easily.

Test Plan: Grepped for cache, created this revision.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T12996

Differential Revision: https://secure.phabricator.com/D18643