Revert "Fix workflow action buttons in awaiting review dashboard panel"

This reverts commit b3846a63fc.

It's a partial revert as the changes to DropdownController itself is
still useful, since it allows us to target the 'shown' event on the more
specific element instead of the document.

wagtail/admin/templates/wagtailadmin/home/workflow_objects_to_moderate.html

@@ -91,12 +91,6 @@
 
     <script src="{% versioned_static 'wagtailadmin/js/workflow-action.js' %}"></script>
     <script>
-        document.querySelectorAll('[data-controller="w-dropdown"]').forEach((e) => {
-            e.addEventListener(
-                'w-dropdown:shown',
-                () => ActivateWorkflowActionsForDashboard('{{ csrf_token|escapejs }}'),
-                { once: true },
-            );
-        });
+        document.addEventListener('DOMContentLoaded', () => ActivateWorkflowActionsForDashboard('{{ csrf_token|escapejs }}'));
     </script>
 {% endif %}