Refactor matrix example to improve clarity and educational value

[Tithi234]

Where to Put New Files

New files should be placed in a top-level subfolder named after the
corresponding article slug. For example:

---

How to Merge Your Changes

1. Ensure that all CI code style checks pass. Run the automatic code formatter if necessary.
   See the repository README for detailed instructions.
2. Request a review from an RP Team member on Slack.
3. After receiving at least one approved review, GitHub will allow you to merge the pull request.
4. 🎉