proxies: registry: let ppc64le builders directly access registry
    
    f39 adds flatpaks for ppc64le, so we need to allow ppc64le builders to
    access the registry directly so they can install flatpaks in the ostree
    install images. Without this they try and get them from the cdn and the
    builder firewall blocks them and it times out and the image fails to
    compose.
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>