Python3.13 support - close_clients #683

Hello!
First of all - thanks for the amazing project.

I am using python3.13 and I noticed that uvloop's Server doesn't have close_clients.

Since running projects with fastapi and uvicorn uses uvloop, it means that any code that uses them might not support python3.13.

The exception I receive is:

AttributeError: 'uvloop.loop.Server' object has no attribute 'close_clients'

And in my humble opinion it should behave as https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.Server.close_clients