Update return_timestamps to true for timestamped model

onnx/generation_config.json

@@ -92,7 +92,7 @@
   "no_timestamps_token_id": 50362,
   "pad_token_id": 50256,
   "prev_sot_token_id": 50360,
-  "return_timestamps": false,
+  "return_timestamps": true,
   "suppress_tokens": [
     1,
     2,