docs(ansible): clarify rmw_implementation manual setup and ROS distro selection (#6750)

Signed-off-by: Mete Fatih Cırıt <mfc@autoware.org>

Author: xmfcx

ansible/roles/rmw_implementation/README.md

@@ -11,13 +11,29 @@ This role sets up ROS 2 RMW implementation following [this page](https://docs.ro
 
 ## Manual Installation
 
-For Universe, the `rosdistro` and `rmw_implementation` variable can also be found in:
-[../../playbooks/universe.yaml](../../playbooks/universe.yaml)
+## Set up the environment variables
+
+Choose **one** ROS distribution and run the corresponding command.
+
+### ROS 2 Humble
+
+```bash
+wget -O /tmp/amd64.env https://raw.githubusercontent.com/autowarefoundation/autoware/main/amd64.env && \
+source /tmp/amd64.env
+```
+
+### ROS 2 Jazzy
 
 ```bash
-wget -O /tmp/amd64.env https://raw.githubusercontent.com/autowarefoundation/autoware/main/amd64.env && source /tmp/amd64.env
+wget -O /tmp/amd64.env https://raw.githubusercontent.com/autowarefoundation/autoware/main/amd64_jazzy.env && \
+source /tmp/amd64.env
+```
+
+## Install the RMW implementation
 
-# For details: https://docs.ros.org/en/humble/How-To-Guides/Working-with-multiple-RMW-implementations.html
+For details: <https://docs.ros.org/en/humble/How-To-Guides/Working-with-multiple-RMW-implementations.html>
+
+```bash
 sudo apt update
 sudo apt install ros-${rosdistro}-${rmw_implementation//_/-}