fix typo

psGrammar/demos/commands.jsgf

@@ -16,4 +16,4 @@ public <command> = [tobi] ( <followMe> | <ordering> | <stack> | <learn> | <rec>
 <save> = (save place);
 <who> = (who are you);
 <gripper> = (show me your gripper);
-<demo> = (end the demo)
+<demo> = (end the demo);