Removed imported symbols that are not accessed or re-exported (#4387)

Co-authored-by: Eric Traut <erictr@microsoft.com>

stdlib/3/asyncio/locks.pyi

@@ -1,9 +1,8 @@
 import sys
 from types import TracebackType
-from typing import Any, Awaitable, Callable, Generator, Iterable, Optional, Type, TypeVar, Union
+from typing import Any, Awaitable, Callable, Generator, Optional, Type, TypeVar, Union
 
 from .events import AbstractEventLoop
-from .futures import Future
 
 _T = TypeVar("_T")
 

stdlib/3/asyncio/protocols.pyi

@@ -1,6 +1,6 @@
 import sys
 from asyncio import transports
-from typing import Optional, Tuple, Union
+from typing import Optional, Tuple
 
 class BaseProtocol:
     def connection_made(self, transport: transports.BaseTransport) -> None: ...