refactor: replace the relations_list with hardcoded links

The relations list was sourced from a context processor. This is
overengineered for a list of two items. We therefore replace the items
with a hardcoded list, which allows us to drop the context processor in
the future.

apis_core/apis_metainfo/templates/base.html

@@ -126,10 +126,10 @@
  <div class="dropdown-menu" aria-labelledby="navbarDropdown">
 
  {% block relations-menu-items %}
- {% for ent in relations_list %}
- <a class="dropdown-item"
-  href="{% url 'apis:apis_relations:generic_relations_list' ent %}">{{ ent|title }}</a>
- {% endfor %}
+ <a class="dropdown-item"
+  href="{% url 'apis:apis_relations:generic_relations_list' "property" %}">Properties</a>
+ <a class="dropdown-item"
+  href="{% url 'apis:apis_relations:generic_relations_list' "triple" %}">Triples</a>
  {% endblock relations-menu-items %}
 
  </div>