autosign: setup to resign f39 packages with f40 key before branching
    
    Branching of f39 is next week, so we need to resign most of everything
    with the f40 key so rawhide can be signed after branching.
    we will need to make another pass after this one is done.
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>