Update styling.md (#4690)

docs/docs/styling.md

     visible: false
   },
   layout: {
-    topMargin: Navigation.constants().statusBarHeight, // Set the layout's top margin
+    topMargin: (await Navigation.constants()).statusBarHeight, // Set the layout's top margin
     orientation: ['portrait', 'landscape'] | ['sensorLandscape'], // An array of supported orientations
     componentBackgroundColor: 'red' // Set background color only for components, helps reduce overdraw if background color is set in default options.
   },