spec: Actually require whatever provides the repoquery command
    
    We actually only require DNF and something that enables
    the 'dnf repoquery' subcommand.
    
    In DNF < 2.0.0, this was in dnf-plugins-core. But since DNF 2.0.0,
    it has been part of DNF itself. This reduces the dependencies
    slightly in this case, making it easier to run in minimal environments.