use <|im_end|> as eos

tokenizer_config.json

@@ -1,7 +1,7 @@
 {
   "add_prefix_space": false,
   "clean_up_tokenization_spaces": true,
-  "eos_token": "<|endoftext|>",
+  "eos_token": "<|im_end|>",
   "model_max_length": 2048,
   "tokenizer_class": "PreTrainedTokenizerFast"
 }