message: Remove trivial tests from SoundsLayer
diff: import { expectType } from 'tsd';
  -expectType<'AmbientSound'>(SoundsLayer.documentName);
  expectType<SoundsLayer | undefined>(SoundsLayer.instance);
  -expectType<SoundsLayer.LayerOptions>(SoundsLayer.layerOptions);
  -expectType<'sounds'>(SoundsLayer.layerOptions.name);
  expectType<typeof AmbientSound>(SoundsLayer.layerOptions.objectClass);
  const layer = new SoundsLayer();
  expectType<typeof AmbientSound>(layer.options.objectClass);
  expectType<SoundsLayer.LayerOptions>(layer.options);
  expectType<'sounds'>(layer.options.name);
  -
  -expectType<boolean>(layer.livePreview);
  -
  -expectType<Promise<SoundsLayer>>(layer.tearDown());
  -
  -expectType<void>(layer.initializeSources());
  -
  -expectType<number | void>(layer.refresh());
  -expectType<number | void>(layer.refresh({}));
  -expectType<number | void>(layer.refresh({ fade: 50 }));
  -
  -expectType<void>(layer.previewSound({ x: 100, y: 0 }));
  -
  -expectType<void>(layer.stopAll());
  