revert name change for Group, GroupMember

these were named as BookwyrmGroup and BookwyrmGroupMember due to a misunderstanding about related_name and a dodgy development environment. This naming makes more sense.

bookwyrm/templates/groups/suggested_users.html

@@ -37,6 +37,6 @@
     {% endfor %}
     {% else %}
     <div >
-      No potential members found for "{{ query }}"
+      <p>No potential members found for "{{ query }}"</p>
     </div>
 {% endif %}