Cleanup linter READMEs

The intro paragraph is duplicated from the main README, and can be
removed. Also, the headings could be bumped from h3s to h2s.

Change-Id: Ib84437b86fc21815fb41c92c1fe83ec5a3ab3c25
Reviewed-on: https://gerrit.causes.com/33677
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>