Update music box recipe

Author: bennuttall

docs/examples/music_box.py

@@ -5,14 +5,12 @@
 
 pygame.mixer.init()
 
-sound_pins = {
-    2: Sound("samples/drum_tom_mid_hard.wav"),
-    3: Sound("samples/drum_cymbal_open.wav"),
+button_sounds = {
+    Button(2): Sound("samples/drum_tom_mid_hard.wav"),
+    Button(3): Sound("samples/drum_cymbal_open.wav"),
 }
 
-buttons = [Button(pin) for pin in sound_pins]
-for button in buttons:
-    sound = sound_pins[button.pin.number]
+for button, sound in button_sounds.items():
     button.when_pressed = sound.play
 
 pause()