docs(README.md): fix sample launch code example (#67)

Signed-off-by: Takamasa Horibe <[email protected]>

README.md

@@ -139,7 +139,7 @@ Suppose that you've set up a workspace.
 
    ```bash
    source install/setup.bash
-   ros2 launch tier4_autoware_launch planning_simulator.launch.xml vehicle_model:=lexus sensor_model:=aip_xx1 map_path:=$HOME/Downloads/sample_map
+   ros2 launch autoware_launch planning_simulator.launch.xml vehicle_model:=sample_vehicle sensor_model:=sample_sensor_kit map_path:=$HOME/Downloads/sample_map
    ```
 
 > Note: More tutorials will be written [here](https://autowarefoundation.github.io/autoware-documentation/tier4-proposal/) soon.