Use typing_extensions.Self in the stdlib (#9694)

stdlib/sunau.pyi

@@ -1,7 +1,7 @@
 import sys
-from _typeshed import Self, Unused
+from _typeshed import Unused
 from typing import IO, Any, NamedTuple, NoReturn, overload
-from typing_extensions import Literal, TypeAlias
+from typing_extensions import Literal, Self, TypeAlias
 
 _File: TypeAlias = str | IO[bytes]
 
@@ -32,7 +32,7 @@ class _sunau_params(NamedTuple):
 
 class Au_read:
     def __init__(self, f: _File) -> None: ...
-    def __enter__(self: Self) -> Self: ...
+    def __enter__(self) -> Self: ...
     def __exit__(self, *args: Unused) -> None: ...
     def getfp(self) -> IO[bytes] | None: ...
     def rewind(self) -> None: ...
@@ -52,7 +52,7 @@ class Au_read:
 
 class Au_write:
     def __init__(self, f: _File) -> None: ...
-    def __enter__(self: Self) -> Self: ...
+    def __enter__(self) -> Self: ...
     def __exit__(self, *args: Unused) -> None: ...
     def setnchannels(self, nchannels: int) -> None: ...
     def getnchannels(self) -> int: ...