update default generation params

generation_config.json

@@ -2,8 +2,12 @@
   "_from_model_config": true,
   "bos_token_id": 0,
   "eos_token_id": 0,
-  "max_new_tokens": 64,
-  "top_k": 4,
-  "penalty_alpha": 0.6,
-  "transformers_version": "4.28.1"
-}
+  "transformers_version": "4.28.1",
+  "use_cache": false,
+  "temperature": 0.1,
+  "top_p": 0.75,
+  "top_k": 40,
+  "num_beams": 4,
+  "max_new_tokens": 128,
+  "max_length": null
+}