Remove `@group` annotations

Summary: I'm pretty sure that `@group` annotations are useless now... I believe that they were originally used by Diviner?

Test Plan: Eye-balled it.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin, aurelijus

Differential Revision: https://secure.phabricator.com/D9855