Remove support for python <3.11 (#1273)

Python 3.11 ships with latest Debian Bookworm. 
pypy is not that widely used with this library based on statistics. It could be added back when pypy supports python 3.11.

tests/test_discovery.py

@@ -7,11 +7,11 @@ import json
 import logging
 import re
 import socket
+from asyncio import timeout as asyncio_timeout
 from unittest.mock import MagicMock
 
 import aiohttp
 import pytest  # type: ignore # https://github.com/pytest-dev/pytest/issues/3342
-from async_timeout import timeout as asyncio_timeout
 from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives.asymmetric import padding as asymmetric_padding