Fix OGG Vorbis playback with more than one channel

When an OGG Vorbis file has more than one channel we accidentily were
assigning only the left channel to both the L and R channels of the
AudioFrame output buffer

modules/vorbis/audio_stream_ogg_vorbis.cpp

@@ -110,7 +110,7 @@ int AudioStreamPlaybackOGGVorbis::_mix_frames_vorbis(AudioFrame *p_buffer, int p
 	if (info.channels > 1) {
 		for (int frame = 0; frame < frames; frame++) {
 			p_buffer[frame].l = pcm[0][frame];
-			p_buffer[frame].r = pcm[0][frame];
+			p_buffer[frame].r = pcm[1][frame];
 		}
 	} else {
 		for (int frame = 0; frame < frames; frame++) {