Fix formatting of description of systemd command

[clebergnu]

When running "podman-compose", the list of commands gets displayed. The systemd command is an outlier, showing multiple lines, IMO unintended at this location.

This change moves the longer command description to its proper place, that is, it gets shown when "podman-compose systemd --help" is executed.

Before this, running podman-compose:

command:
  {help,version,wait,systemd,pull,push,build,up,down,ps,run,exec,start,stop,restart,logs,config,port,pause,unpause,kill}
    help                show help
    version             show version
    wait                wait running containers to stop
    systemd             create systemd unit file and register its compose stacks
                        
                            When first installed type `sudo podman-compose systemd -a create-unit`
                            later you can add a compose stack by running `podman-compose systemd -a register`
                            then you can start/stop your stack with `systemctl --user start podman-compose@<PROJ>`
                            
    pull                pull stack images
    push                push stack images
...

After this, running podman-compose:

...
command:
  {help,version,wait,systemd,pull,push,build,up,down,ps,run,exec,start,stop,restart,logs,config,port,pause,unpause,kill}
    help                show help
    version             show version
    wait                wait running containers to stop
    systemd             create systemd unit file and register its compose stacks
    pull                pull stack images
    push                push stack images
...

And when running podman-compose systemd --help:

usage: podman-compose systemd [-h] [-a {register,create-unit,list,ls}]

When first installed type `sudo podman-compose systemd -a create-unit` later
you can add a compose stack by running `podman-compose systemd -a register`
then you can start/stop your stack with `systemctl --user start podman-
compose@<PROJ>`

options:
  -h, --help            show this help message and exit
  -a {register,create-unit,list,ls}, --action {register,create-unit,list,ls}
                        create systemd unit file or register compose stack to
                        it

[clebergnu]

gentle ping @muayyad-alsadi , can you help with review here?

[muayyad-alsadi]

Please fix styling using black

[p12tic]

Needs rebase on top of latest main. Also needs reformatting.