PlayerComponent: fix general multichannel failure

Caused by my own stupidity and inability to deal with my own API
changes. While the code "should" work, it still won't until the
deprecation of the old semantics of the "audio-channels" property is
finished and the new behavior is default.

src/player/PlayerComponent.cpp

@@ -933,7 +933,7 @@ void PlayerComponent::setAudioConfiguration()
   if (deviceType == AUDIO_DEVICE_TYPE_SPDIF)
     layout = "2.0";
 
-  mpv::qt::set_property(m_mpv, "audio-channels", layout);
+  mpv::qt::set_option_variant(m_mpv, "audio-channels", layout);
 
   // if the user has indicated that PCM only works for stereo, and that
   // the receiver supports AC3, set this extra option that allows us to transcode