Drop an old unnecessary workaround
    
    This is another use of blacklist, but the entire workaround has
    been obsolete since a day after it was added, per
    https://pagure.io/fedora-infrastructure/issue/8096 . I double
    checked and the mirror still exists and is still up to date.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>