Remove unused formset.permission_types code in workflow_pages_formset.html template

The workflow pages formset never defines permission_types (and has no business to do so).

It's likely that this template was copy-pasted from the page_permissions_formset.html template.

wagtail/admin/templates/wagtailadmin/workflows/includes/workflow_pages_formset.html

@@ -17,9 +17,6 @@
     <thead>
         <tr>
             <th>{% trans "Page" %}</th>
-            {% for identifier, short_label, long_label in formset.permission_types %}
-                <th title="{{ long_label }}">{{ short_label }}</th>
-            {% endfor %}
             <th></th>
         </tr>
     </thead>