Docs: fix dead link in router.md (#3799)

docs/router/router.md

@@ -10,7 +10,7 @@ The router is an independent Python package, and it can be used as a drop-in rep
 pip install sglang-router
 ```
 
-Detailed usage of the router can be found in [launch_router](https://github.com/sgl-project/sglang/blob/main/sgl-router/py_src/sglang_router/launch_router.py) and [launch_server](https://github.com/sgl-project/sglang/blob/main/sgl-router/py_src/sglang/launch_server.py). Also, you can directly run the following command to see the usage of the router.
+Detailed usage of the router can be found in [launch_router](https://github.com/sgl-project/sglang/blob/main/sgl-router/py_src/sglang_router/launch_router.py) and [launch_server](https://github.com/sgl-project/sglang/blob/main/sgl-router/py_src/sglang_router/launch_server.py). Also, you can directly run the following command to see the usage of the router.
 
 ```bash
 python -m sglang_router.launch_server --help