fix dataset_config

dataset_config/multiwoz21.json

@@ -7,7 +7,7 @@
     "false",
     "refer",
     "inform"
-  ]
+  ],
   "slots": [
     "taxi-leaveAt",
     "taxi-destination",
@@ -39,7 +39,7 @@
     "train-day",
     "train-arriveBy",
     "train-departure"
-  ]
+  ],
   "label_maps": {
     "guest house": [
       "guest houses"