removed extrfilea manifest

Author: tomitavela

iframe-sandbox-app/public/index.html

@@ -13,8 +13,9 @@
     <!--
       manifest.json provides metadata used when your web app is installed on a
       user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/
-    -->
+   
     <link rel="manifest" href="%PUBLIC_URL%/manifest.json" />
+     -->
     <!--
       Notice the use of %PUBLIC_URL% in the tags above.
       It will be replaced with the URL of the `public` folder during the build.