Update config.json

config.json

@@ -125,6 +125,6 @@
   "is_encoder_decoder": true,
   "max_length": 142,
   "min_length": 56,
-  "model_type": "encoder_decoder",
+  "model_type": "encoder-decoder",
   "no_repeat_ngram_size": 3
-}
+}