Update mainboard.md

docs/hardware/mainboard.md

@@ -20,7 +20,7 @@ It also offers a built in Realtek WiFi chip ([RTL8723DU](https://www.realtek.com
 
 At the following picture I added labels of the connectors.  
 
-![Mainboard labeled](../assets/images/mainboard_K2Pro_labeled_web.jpg)
+![Mainboard labeled](../assets/images/mainboard_K2Plus_labeled_web.jpg)
 
 The pinout of the 7 pin connector of the acceleration sensor is printed onto the PCB itself (same with some other pinouts of connectors in that row), but I'll list it here again, just in case you can't read it on your mainboard and when zooming in the picture shown above.  
 So when you're looking at the connector in the direction of the picture above, the pinout (from left to right) is: