Update tokenizer_config.json

tokenizer_config.json

@@ -3,7 +3,7 @@
   "bos_token": "<|endoftext|>",
   "clean_up_tokenization_spaces": false,
   "eos_token": "<|endoftext|>",
-  "model_max_length": 1024,
+  "model_max_length": 4096,
   "tokenizer_class": "GPT2Tokenizer",
   "unk_token": "<|endoftext|>"
 }