fix(FEC-8308): audio track changes are not reproted (#7)

Audio track change was not reported due to incorrect event handler.

src/kava.js

@@ -307,7 +307,7 @@ export default class Kava extends BasePlugin {
   }
 
   _onAudioTrackChanged(event: FakeEvent): void {
-    const audioTrack = event.payload.selectedVideoTrack;
+    const audioTrack = event.payload.selectedAudioTrack;
     this._model.updateModel({language: audioTrack.language});
     this._sendAnalytics(KavaEventModel.AUDIO_SELECTED);
   }