Bump mail_room to 0.0.4

MR to bump in our codebase: gitlab-org/gitlab!31188 (merged)

MR in our fork: https://gitlab.com/gitlab-org/gitlab-mail_room/-/merge_requests/9, mirroring https://github.com/tpitale/mail_room/pull/110 upstream.

See gitlab-com/gl-infra/scalability#317 (closed)