ipa-advise: remove plugin config-fedora-authconfig
    
    ipa-advise config-fedora-authconfig produces a script with authconfig
    instructions for configuring Fedora 18/19 client with IPA server
    without use of SSSD. Fedora 18 and 19 are not supported any more,
    so the plugin could be removed.
    
    Resolves: https://pagure.io/freeipa/issue/7533
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>