Add Geo replication for custom emojis

The following discussion from gitlab-ce!14609 should be addressed:

• @toon started a discussion: (+1 comment)

  You'll need Geo replication for these custom emojis too: https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/services/geo/file_service.rb#L5 (you should double check if that's all you need 😝).