Use typing_extensions.Self instead of _typeshed.Self (#9702)

stubs/pysftp/pysftp/__init__.pyi

@@ -1,10 +1,9 @@
-from _typeshed import Self
 from collections.abc import Callable, Sequence
 from contextlib import AbstractContextManager
 from stat import S_IMODE as S_IMODE
 from types import TracebackType
 from typing import IO
-from typing_extensions import Literal, TypeAlias
+from typing_extensions import Literal, Self, TypeAlias
 
 import paramiko
 from paramiko import AuthenticationException as AuthenticationException
@@ -123,7 +122,7 @@ class Connection:
     @property
     def remote_server_key(self) -> paramiko.PKey: ...
     def __del__(self) -> None: ...
-    def __enter__(self: Self) -> Self: ...
+    def __enter__(self) -> Self: ...
     def __exit__(
         self, etype: type[BaseException] | None, value: BaseException | None, traceback: TracebackType | None
     ) -> None: ...