Remove old duplicate test for end of MIDI playback...

... which, anyway, had errors introduced into it (realTime mistakenly used as a
duration)

src/AudioIOBase.h

@@ -436,10 +436,6 @@ protected:
       // playback ring buffers, during usual straight or looping play
       void TrackTimeUpdate(double realElapsed);
 
-      // Convert a nonnegative real duration to an increment of track time
-      // relative to mT0.
-      double TrackDuration(double realElapsed) const;
-
       // Convert time between mT0 and argument to real duration, according to
       // time track if one is given; result is always nonnegative
       double RealDuration(double trackTime1) const;