Align label mapping with imdb dataset

Hi there, your model is using a default label mapping. Accept this PR to align the label mapping with the imdb dataset this model was trained on. This will enable your model to be evaluated by [Hugging Face's automatic model evaluator](https://huggingface.co/spaces/autoevaluate/model-evaluator?dataset=imdb)

config.json

@@ -9,13 +9,13 @@
   "dropout": 0.1,
   "hidden_dim": 3072,
   "id2label": {
-    "0": "LABEL_0",
-    "1": "LABEL_1"
+    "0": "neg",
+    "1": "pos"
   },
   "initializer_range": 0.02,
   "label2id": {
-    "LABEL_0": 0,
-    "LABEL_1": 1
+    "neg": 0,
+    "pos": 1
   },
   "max_position_embeddings": 512,
   "model_type": "distilbert",