update default generate hyperparams

generation_config.json

@@ -6,6 +6,7 @@
   "max_new_tokens": 512,
   "do_sample": true,
   "top_k": 0,
-  "top_p": 0.5,
+  "top_p": 0.8,
+  "repetition_penalty": 1.1,
   "transformers_version": "4.31.0"
 }