docs: wrong command in structured_outputs README (#26677)

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

examples/online_serving/structured_outputs/README.md

@@ -21,7 +21,7 @@ If you want to run this script standalone with `uv`, you can use the following:
 
 ```bash
 uvx --from git+https://github.com/vllm-project/vllm#subdirectory=examples/online_serving/structured_outputs \
-    structured-output
+    structured-outputs
 ```
 
 See [feature docs](https://docs.vllm.ai/en/latest/features/structured_outputs.html) for more information.