Update build requirements on twine
    
    On Fedora >= 29 the command 'twine' is provied by the twine package. On
    F28 it's in python3-twine. F30 no longer has python3-twine.
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>