Apply ruff/Pyflakes rule F401

F401 imported but unused

Author: DimitriPapadopoulos

tests/test_tcp.py

@@ -1,5 +1,4 @@
 import asyncio
-import asyncio.sslproto
 import gc
 import os
 import select

uvloop/_testbase.py

@@ -2,7 +2,6 @@
 
 
 import asyncio
-import asyncio.events
 import collections
 import contextlib
 import gc

uvloop/loop.pyi

@@ -1,6 +1,5 @@
 import asyncio
 import ssl
-import sys
 from socket import AddressFamily, SocketKind, _Address, _RetAddress, socket
 from typing import (
     IO,