Pim 2712

| Q                    | A
| -------------------- | ---
| Bug fix?             | No
| New feature?         | No
| BC breaks?           | No
| CI currently passes? | 
| Tests pass?          | Yes
| Scenarios pass?      | Yes
| Checkstyle issues?   | No
| Changelog updated?   | Yes
| Fixed tickets        | PIM-2712
| Doc PR               | 
Don't understand why you created this method and set it as public.

Otherwise, it seems better to use ChannelManager::getChannels() or directly inject ChannelRepository. ManagerRegistry should be use for entities which can be stored in MongoDB or ORM