Fix the header template of the docker-setup hook

[fabiosammy]

I know that is a very simple PR, but I lot like 40 minutes before realized that the issue was this header from the template :sweat_smile:

[plattenschieber]

Coming from python, I really thought it should be a ruby script and that it uses an internal ssh library 😅 Thanks for making this clear @fabiosammy 🙌