[paramiko] Transport.open_sftp_client never returns None (#16567)

Author: jacobglikz

stubs/paramiko/paramiko/transport.pyi

@@ -127,7 +127,7 @@ class Transport(Thread, ClosingContextManager):
         self, address: str, port: int, handler: Callable[[Channel, _Addr, _Addr], object] | None = None
     ) -> int: ...
     def cancel_port_forward(self, address: str, port: int) -> None: ...
-    def open_sftp_client(self) -> SFTPClient | None: ...
+    def open_sftp_client(self) -> SFTPClient: ...
     def send_ignore(self, byte_count: int | None = None) -> None: ...
     def renegotiate_keys(self) -> None: ...
     def set_keepalive(self, interval: float) -> None: ...