Remove setting the script tag to async (#1701)

By default, loading the script using the inline method makes the
script async. Hence, setting the async attribute makes it fail for
instances where the loader is not set to work asnc

Author: musale

packages/mgt/src/bundle/mgt-loader.js

@@ -46,7 +46,6 @@
 
   function addScript(src, onload) {
     var tag = document.createElement('script');
-    tag.setAttribute('async', '');
     tag.setAttribute('src', encodeURI(src));
 
     // if (onload) {