Align label mapping with amazon_polarity dataset

config.json

@@ -23,5 +23,13 @@
   "transformers_version": "4.10.2",
   "type_vocab_size": 2,
   "use_cache": true,
-  "vocab_size": 30522
-}
+  "vocab_size": 30522,
+  "label2id": {
+    "negative": 0,
+    "positive": 1
+  },
+  "id2label": {
+    "0": "negative",
+    "1": "positive"
+  }
+}