chore: fix lint errors in mqtt channel

Author: allenporter

roborock/devices/mqtt_channel.py

@@ -76,7 +76,7 @@ async def subscribe(self, callback: Callable[[RoborockMessage], None]) -> Callab
 
     async def subscribe_stream(self) -> AsyncGenerator[RoborockMessage, None]:
         """Subscribe to the device's message stream.
-        
+
         This is useful for processing all incoming messages in an async for loop,
         when they are not necessarily associated with a specific request.
         """