Add gpt2 tokenizer: tokenizer_config.json

tokenizer_config.json

@@ -8,9 +8,5 @@
   "model_max_length": 1024,
   "pad_token": null,
   "tokenizer_class": "GPT2Tokenizer",
-  "unk_token": "<|endoftext|>",
-  "auto_map": {
-    "AutoConfig": "modeling_loop_lm.LoopLMConfig",
-    "AutoModelForCausalLM": "modeling_loop_lm.LoopLMForCausalLM"
-  }
-}
+  "unk_token": "<|endoftext|>"
+}