Improve logging of Celery in Docker

[nijel]

Describe the problem

Not sore whether is configuration issue, or general behavior, but #9128 shows most of Celery logs doubled. Seems like it is going once through Celery configuration and once through Weblate one:

celery-celery stderr | [2023-04-20 16:48:28,686: DEBUG/399] Renewal thread for Lock('lock:lock:repo:5') exited.
celery-celery stderr | [2023-04-20 16:48:28,686: DEBUG/ForkPoolWorker-1] Renewal thread for Lock('lock:lock:repo:5') exited.

Describe the solution you'd like

Only one log entry should be shown for each event.

Describe alternatives you've considered

No response

Screenshots

No response

Additional context

No response