updated setPitch documentation

Author: Nitesh639

src/soundfile.js

@@ -885,13 +885,12 @@ class SoundFile {
     return this.playbackRate;
   }
 
-  // TO DO: document this
   /**
-   *  Pitch rate of a sound file can be changed by providing a MIDI note number.
+   *  Pitch of a sound file can be changed by providing a MIDI note number.
    *  It will change the pitch and also the speed.
    *  If the input note is 60 (middle C), then frequency and speed is normal.
    *  If we increase the note input, then frequency and speed increases,
-   *  and If we decrease the note input, then frequency and speed decreases.
+   *  and if we decrease the note input, then frequency and speed decreases.
    *
    *  @method setPitch
    *  @for p5.SoundFile