Fixed responsive example in documentation

This fixes the documentation so the responsive example actually works.
Everything was working properly, the example just wasn't updated when
the default for the width was changed to `100%` in
select2@5fd72d2.
This is a change from the old `resolve` width setting, which is
responsible for parsing the style attribute and getting the width that
was set.

This closes select2#4050

Author: kevin-brown

docs/examples.html

@@ -201,7 +201,9 @@ <h1>
     $(".js-example-disabled").select2();
     $(".js-example-disabled-multi").select2();
 
-    $(".js-example-responsive").select2();
+    $(".js-example-responsive").select2({
+        width: 'resolve' // need to override the changed default
+    });
 
     $disabledResults.select2();