unbound have no uninstall/removal documentation

[icf20]

According to reddit something like this should be in the documentation

    Stop the service:
    sudo service unbound stop
    Remove unbound package:
    sudo apt remove unbound
    Remove configs and properties:
    sudo rm -r /var/lib/unbound/
    sudo rm -r /etc/unbound/
    Remove dependencies that are not needed anymore:
    sudo apt autoremove
    Clean up:
    sudo apt autoclean

[yubiuser]

I think stopping the service is not necessary as it will be stopped by apt during removal. This PR adds a small note to the guide: #555

IMHO, cleaning and autoremove apt cache are beyond the scope of a installation guide of a recursive DNS server.