add pad_token_id to model’s generation_config.json to fix warning

generation_config.json

@@ -1,6 +1,7 @@
 {
   "_from_model_config": true,
   "eos_token_id": 2,
+  "pad_token_id": 0,
   "transformers_version": "4.55.0",
   "use_cache": false
 }