Update type declaration for Server.sockets.

This is the latest version from typeshed.

Author: aaugustin

src/websockets/asyncio/server.py

@@ -554,7 +554,7 @@ async def serve_forever(self) -> None:  # pragma: no cover
         await self.server.serve_forever()
 
     @property
-    def sockets(self) -> Iterable[socket.socket]:
+    def sockets(self) -> tuple[socket.socket, ...]:
         """
         See :attr:`asyncio.Server.sockets`.