Update config.json

Updating config.json to include right max_position_embeddings size of 512, instead of 514. When using more then 512 tokens a error is generated.

--> Libaries like FastChat use the max_position_embeddings to define the number of tokens that can be used. In this case it should be 512.

config.json

@@ -13,7 +13,7 @@
   "initializer_range": 0.02,
   "intermediate_size": 4096,
   "layer_norm_eps": 1e-05,
-  "max_position_embeddings": 514,
+  "max_position_embeddings": 512,
   "model_type": "xlm-roberta",
   "num_attention_heads": 16,
   "num_hidden_layers": 24,