auth: remove redundant --no-config from commands

auth: remove redundant --no-config from commands

Both the flags --no-config and --config=default prevent the loading of
configuration files from disk when used independently as per
https://github.com/PowerDNS/pdns/blob/master/pdns/receiver.cc#L418-L419

This commit removes the anomaly from documentation and build files to avoid
confusion and make it consistent among all packages.