[pylint] Implement modified-iterating-set (E4703)

[hikaru-kajita]

Summary

Implement E4703 in the issue #970.
Relevant pylint docs is here: https://pylint.readthedocs.io/en/stable/user_guide/messages/error/modified-iterating-set.html

Test Plan

I've written it in the modified_iterating_set.py.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.