improve: add ethernet deinit to example (IDFGH-11704)

[elton-a-vieira]

On the idf 5.1, the Ethernet driver has an internal counter that will be initialized at esp_eth_driver_install and will be incremented at esp_eth_new_netif_glue.

To perform a successful ethernet deinit the counter must be cleared and it is done by esp_eth_del_netif_glue which decrements the counter dealing to successful esp_eth_driver_uninstall.

This procedure was unclear in the previous code sample.

[CLAassistant]

All committers have signed the CLA.

[github-actions]

	Messages
📖	🎉 Good Job! All checks are passing!

👋 Hello elton-a-vieira, we appreciate your contribution to this project!

---

📘 Please review the project's Contributions Guide for key guidelines on code, documentation, testing, and more.

---

🖊️ Please also make sure you have read and signed the Contributor License Agreement for this project.

---

Click to see more instructions ...

This automated output is generated by the PR linter DangerJS, which checks if your Pull Request meets the project's requirements and helps you fix potential issues.

DangerJS is triggered with each push event to a Pull Request and modify the contents of this comment.

Please consider the following:
- Danger mainly focuses on the PR structure and formatting and can't understand the meaning behind your code or changes.
- Danger is not a substitute for human code reviews; it's still important to request a code review from your colleagues.
- To manually retry these Danger checks, please navigate to the Actions tab and re-run last Danger workflow.

Review and merge process you can expect ...

We do welcome contributions in the form of bug reports, feature requests and pull requests via this public GitHub repository.

This GitHub project is public mirror of our internal git repository

1. An internal issue has been created for the PR, we assign it to the relevant engineer.
2. They review the PR and either approve it or ask you for changes or clarifications.
3. Once the GitHub PR is approved, we synchronize it into our internal git repository.
4. In the internal git repository we do the final review, collect approvals from core owners and make sure all the automated tests are passing.
- At this point we may do some adjustments to the proposed change, or extend it by adding tests or documentation.
5. If the change is approved and passes the tests it is merged into the default branch.
5. On next sync from the internal git repository merged change will appear in this public GitHub repository.

Generated by 🚫 dangerJS against 2d320f5

[kostaond]

@elton-a-vieira thank you very much for your contribution! Unfortunately, the actual solution of described issue requires more complex update. The update will be provided soon. Please see #13443 for additional information.