net/traefik: Update to upstream version 2.9.4

Details:

• Update to 2.9.x branch: https://github.com/traefik/traefik/releases/tag/v2.9.4
• No breaking config changes, see https://doc.traefik.io/traefik/migration/v2/#v29
• but "Traefik Pilot" has been removed.

MFH: 2022Q4