Remove version from docker compose file

[nook24]

The version directive is obsolete and should be removed from the docker-compose file.
Honestly I don't know if other compose implementations rely on it. We should probably wait a few month before removing it.
Probably also a good idea to spin up a podman-compose or any other alternative compose implementation for testing.

WARN[0000] /root/openITCOCKPIT-ce-docker/compose.yml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion

https://docs.docker.com/reference/compose-file/version-and-name/