update generation config

generation_config.json

@@ -2,6 +2,9 @@
   "_from_model_config": true,
   "bos_token_id": 2048,
   "decoder_start_token_id": 2048,
+  "do_sample": true,
+  "guidance_scale": 3.0,
+  "max_length": 1500,
   "pad_token_id": 2048,
   "transformers_version": "4.31.0.dev0"
 }