retire_packagers: fix the reason for which a package is orphaned
    
    Cf the code at:
    https://pagure.io/pagure-dist-git/blob/master/f/pagure_distgit/forms.py#_33
    
    fixes https://pagure.io/releng/issue/9987
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>