fix digital ch

Author: karlsoderby

content/micropython/02.micropython-course/course/04.digital/03.digital.md

@@ -23,7 +23,7 @@ So how does digital signals work? Well, it is quite simple! In the case of the b
 For the LED, we can do sort of the reverse: we can write a HIGH / LOW state to it. If we connect the LED to a **digital pin** on the Arduino, we can therefore turn it on or off, by writing a **"1"** or **"0"** to it.
 
 <video width="100%" loop autoplay>
-<source src="assets/button+led.mp4" type="video/mp4" />
+<source src="assets/button-led.mp4" type="video/mp4" />
 </video>
 
 ## Exercise 1: Read a Button