Remove HeraldContentTypeConfig and move repetition to Adapters

Summary: Ref T2769. Get rid of the last use of HeraldContentTypeConfig by moving repetition options into Adapters.

Test Plan: Viewed / edited Herald rules.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2769

Differential Revision: https://secure.phabricator.com/D6664