docs: broken formatting

Code blocks in [docs](https://docs.aiogram.dev/en/dev-3.x/dispatcher/router.html#nested-routers) are broken

![Image](https://github.com/user-attachments/assets/4e54a1bf-0e80-4163-bd6d-5375ca5e500b)