removed async keyword

lib/lazy/content-lazy-loader.js

@@ -28,7 +28,7 @@ this.lazyLoader = this.lazyLoader || (() => {
 
 	return { process };
 
-	async function process() {
+	function process() {
 		return new Promise(resolve => {
 			let timeoutId, maxTimeoutId, idleTimeoutId, srcAttributeChanged;
 			const observer = new MutationObserver(() => {