Small fixes to the spec file for Pagure 5.2.x
    
    There were a few Python shebangs not being changed properly and the
    systemd timer for the pull mirror service wasn't being properly
    addressed in the scriptlets for the spec.
    
    In addition, the RHEL conditionals have been adjusted to account for
    RHEL 8.
    
    Signed-off-by: Neal Gompa <ngompa13@gmail.com></ngompa13@gmail.com>