Update config.json

remove `"xla_device": true` to remove warning.

config.json

@@ -21,6 +21,5 @@
   "num_hidden_layers": 12,
   "pad_token_id": 1,
   "type_vocab_size": 1,
-  "vocab_size": 50265,
-  "xla_device": true
+  "vocab_size": 50265
 }