spec file: force nodejs < 20 on fedora < 39
    
    On fedora < 39, nodejs 20 is not the default version. As
    a consequence, the installation of nodejs20 adds the command
    /usr/bin/node-20 instead of /usr/bin/node.
    FreeIPA build is using the node command and fails if the
    command is missing.
    
    Force nodejs < 20 on fedora < 39 to make sure the node
    command is installed.
    
    Fixes: https://pagure.io/freeipa/issue/9374
    
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>