Change "master" to "main" when git-cloning github.com/wildfly/wildfly

As the "master" branch has been renamed to "main" in the github.com/wildfly/wildfly repository, the same modification should be carried out in the Narayana codebase (e.g. "narayana.sh" and "narayana-release-process.sh"). Please, double check what files should also be modified.