Fix link to PitchFollower tutorial

Previously, the link pointed to the ToneMelody tutorial, which already has a link on the tone reference page.

Author: per1234

Language/Functions/Advanced IO/tone.adoc

@@ -78,7 +78,7 @@ If you want to play different pitches on multiple pins, you need to call `noTone
 
 [role="example"]
 * #EXAMPLE# http://arduino.cc/en/Tutorial/Tone[Tone^]
-* #EXAMPLE# http://arduino.cc/en/Tutorial/Tone[Pitch follower^]
+* #EXAMPLE# http://arduino.cc/en/Tutorial/tonePitchFollower[Pitch follower^]
 * #EXAMPLE# http://arduino.cc/en/Tutorial/Tone3[Simple Keyboard^]
 * #EXAMPLE# http://arduino.cc/en/Tutorial/Tone4[multiple tones^]
 * #EXAMPLE# http://arduino.cc/en/Tutorial/PWM[PWM^]