17422 update custom field group display tag (#17423)

* 17422 update custom field group display tag

* 17422 review changes

netbox/utilities/templates/form_helpers/render_custom_fields.html

@@ -3,7 +3,7 @@
 {% for group, fields in form.custom_field_groups.items %}
   {% if group %}
   <div class="row">
-    <h6 class="offset-sm-3 mb-3">{{ group }}</h6>
+    <h3 class="col-9 offset-3 mb-3 h4">{{ group }}</h3>
   </div>
   {% endif %}
   {% for name in fields %}