fix: use logger instance instead of logging module in streamable_http

Author: Edison-A-N

src/mcp/server/streamable_http.py

@@ -870,16 +870,16 @@ async def message_router():
                                 # Stream might be closed, remove from registry
                                 self._request_streams.pop(request_stream_id, None)
                         else:
-                            logging.debug(
+                            logger.debug(
                                 f"""Request stream {request_stream_id} not found 
                                 for message. Still processing message as the client
                                 might reconnect and replay."""
                             )
                 except anyio.ClosedResourceError:
                     if self._terminated:
-                        logging.debug("Read stream closed by client")
+                        logger.debug("Read stream closed by client")
                     else:
-                        logging.exception("Unexpected closure of read stream in message router")
+                        logger.exception("Unexpected closure of read stream in message router")
                 except Exception:
                     logger.exception("Error in message router")