remove obsolete template (#9596)

data/themes/gadjo/templates/combo/placeholder.html

@@ -1,8 +0,0 @@
-{% load combo %}
-{% for cell in cells %}
-<div class="cell {{ cell.css_class_name }} {% if cell.slug %}{{cell.slug}}{% endif %}"
-     data-ajax-cell-url="{% url 'combo-public-ajax-page-cell' page_pk=page.id cell_reference=cell.get_reference %}"
-     {% if cell.ajax_refresh %}
-     data-ajax-cell-refresh="{{ cell.ajax_refresh }}"
-     {% endif %}><div>{% render_cell cell %}</div></div>
-{% endfor %}