fix: Fixes two minor strict-TS errors.

Author: willum070

samples/layer-traffic/index.ts

@@ -8,15 +8,14 @@
 async function initMap(): Promise<void> {
     await google.maps.importLibrary('maps');
 
-    const mapElement = document.querySelector(
-        'gmp-map'
-    ) as google.maps.MapElement;
+    const mapElement =
+        document.querySelector<google.maps.MapElement>('gmp-map')!;
     const innerMap = mapElement.innerMap;
 
     const trafficLayer = new google.maps.TrafficLayer();
 
     trafficLayer.setMap(innerMap);
 }
 
-initMap();
+void initMap();
 // [END maps_layer_traffic]