Remove registry parameters from automatic installer

From the fact that the git clone and the docker pull commands on the SPHN Connector public repo does not require login anymore I removed the registry relate parameter in the automatic installer script. As you developed it, @katie.kalt please give a quick look at the changes and let me know if you think they're fine. Thanks.

Changes in the documentation can be checked and approved here: https://docs.google.com/document/d/1KzxE0SSp7u5Dmz8QyjM4y42DS4nJ3oYW/edit