retire_packagers: Use the dist-git's specific endpoint to orphan packages
    
    This endpoint is specific to dist-git and does more than the usual
    endpoint by ensuring that the former main admin is removed from the
    project as well as resetting their watch status (so we no longer have
    to make an extra request for this).
    
    It also announces that the package was orphaned on fedora-messaging and
    we are working on automatically notifying the devel list when a package
    is orphaned so people are aware of it as soon as possible and can decide
    if they want to pick it up or not.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>