Fix example.

Change was needed for previous MicroPython beta updates.

Author: microbit-matt-hillsdon

src/examples/sound_effects_user.py

@@ -8,8 +8,8 @@
         duration=500,
         vol_start=100,
         vol_end=255,
-        wave=audio.SoundEffect.WAVE_TRIANGLE,
+        wave=audio.SoundEffect.WAVEFORM_TRIANGLE,
         fx=audio.SoundEffect.FX_VIBRATO,
         shape=audio.SoundEffect.SHAPE_LOG,
     )
-)
+)