PulseAudio: remove debug warning of Underrun

The QAudio::UnderrunError is a normal error and is already reported
to the user.

Change-Id: I0ee5d827666fb08b5eb199255b3b3c5610f743c2
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

src/plugins/pulseaudio/qaudiooutput_pulse.cpp

@@ -85,7 +85,6 @@ static void outputStreamUnderflowCallback(pa_stream *stream, void *userdata)
 {
     Q_UNUSED(stream)
     ((QPulseAudioOutput*)userdata)->streamUnderflowCallback();
-    qWarning() << "Got a buffer underflow!";
 }
 
 static void outputStreamOverflowCallback(pa_stream *stream, void *userdata)