Update subdomain-availability.js

Author: wdhdev

index.html

@@ -54,7 +54,7 @@ <h3>Grab your own sweet-looking <span>.is-a.dev</span> subdomain.</h3>
             </p>
 
             <script async type="text/javascript"
-                src="//cdn.carbonads.com/carbon.js?serve=CW7DE2JU&placement=is-adev&format=cover"
+                src="//cdn.carbonads.com/carbon.js?serve=CW7DE2JU&placement=is-adev&format=responsive"
                 id="_carbonads_js"></script>
 
             <h2>Check Subdomain Availability</h2>