Adjust grammar for the challenge

psGrammar/challenge/team2/order.jsgf

 #JSGF V1.0;
 grammar ordering;
 public <ordering> = [tobi] <order>;
-public <table> = [at table] <number>;
 
 <order> = [please] bring [me] [a] <drink>;
 
-<drink> = (coconut_milk | tea | coke | fanta | water | orange_juice);
+<drink> = (coke | malz | lemonade | water | (ice tea) | coffee);
 
-<number> = (a | b);