Update setup.md (#330)

Author: mrpropellers

tutorials/ros_unity_integration/setup.md

@@ -71,7 +71,7 @@ Follow these steps if using ROS2:
 
    This should build a docker image and start it.
 
-   b) Alternatively, if you're not going to use the Docker image, download the [ROS2 branch of the ROS-TCP-Endpoint](https://github.com/Unity-Technologies/ROS-TCP-Endpoint/tree/ROS2) repository and copy it into the `src` folder in your Colcon workspace. Then navigate to your Colcon workspace and run the following commands:
+   b) Alternatively, if you're not going to use the Docker image, download the [ROS2 branch of the ROS-TCP-Endpoint](https://github.com/Unity-Technologies/ROS-TCP-Endpoint/tree/main-ros2) repository and copy it into the `src` folder in your Colcon workspace. Then navigate to your Colcon workspace and run the following commands:
 
     ```bash
 	source install/setup.bash