Remove obsolete `ffrun` sub-command

src/shellfu/saturnin.sh

         _ls_subcommands)    saturnin__lssc ;;
         _lsfun)             shellfu-get lsfun ;;
         _lsmod)             shellfu-get lsmod ;;
-        _ffrun)             ffrun "$@" ;;
         *)                  saturnin__runsc "$subcommand" "$@" ;;
     esac
 }