Use typing_extensions.Self in the stdlib (#9694)

stdlib/asyncio/streams.pyi

@@ -1,9 +1,9 @@
 import ssl
 import sys
-from _typeshed import Self, StrPath
+from _typeshed import StrPath
 from collections.abc import AsyncIterator, Awaitable, Callable, Iterable, Sequence
 from typing import Any
-from typing_extensions import SupportsIndex, TypeAlias
+from typing_extensions import Self, SupportsIndex, TypeAlias
 
 from . import events, protocols, transports
 from .base_events import Server
@@ -166,5 +166,5 @@ class StreamReader(AsyncIterator[bytes]):
     async def readuntil(self, separator: bytes | bytearray | memoryview = b"\n") -> bytes: ...
     async def read(self, n: int = -1) -> bytes: ...
     async def readexactly(self, n: int) -> bytes: ...
-    def __aiter__(self: Self) -> Self: ...
+    def __aiter__(self) -> Self: ...
     async def __anext__(self) -> bytes: ...