Update vLLM video media I/O arguments

Remove the explicit video fps override and retain only num_frames=256 in --media-io-kwargs.

README.md

@@ -641,7 +641,7 @@ vllm serve nvidia/Cosmos3-Edge \
   --max-model-len 131072 \
   --allowed-local-media-path / \
   --mm-processor-kwargs '{"do_resize": true, "min_pixels": 4096, "max_pixels": 16777216}' \
-  --media-io-kwargs '{"video": {"fps": -1, "num_frames": 256}}'
+  --media-io-kwargs '{"video": {"num_frames": 256}}'
 ```
 
 #### Examples