Fix a typo in `replace` rule of 50-ipaconfig.update
    
    According to ipaserver/install/ldapupdate.py, the format of `replace`
    action (during a parsing of update files) should be `old::new`.
    
    By now, the value to be replaced on is 'ipaSELinuxUserMapOrder: guest_u$$...',
    while it should be 'guest_u$$...'.
    
    Fixes: https://pagure.io/freeipa/issue/7996
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>