docs(setup): Remove deprecated version from docker-compose.yml

[jonasrdl]

You can see the following warning when using the provided docker-compose.yml from the setup instructions:

WARN[0000] ~/nginx-proxy-manager/docker-compose.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion

Since the version is deprecated, it can be removed from the manifest.

[nginxproxymanagerci]

Docker Image for build 1 is available on
DockerHub
as nginxproxymanager/nginx-proxy-manager-dev:pr-4126

Note: ensure you backup your NPM instance before testing this image! Especially if there are database changes
Note: this is a different docker image namespace than the official image