fix member pagination on OER show pages

Pagination was attempting to act upon a local variable that didn't
exist; it was removed in this commit:
- notch8/palni-palci@fbe9093

Replace it with the presenter method that Hyrax typically uses to
display member presenters

app/views/hyrax/oers/_related_items.html.erb

@@ -32,7 +32,7 @@
   <div class="row">
     <% if presenter.total_pages > 1 %>
         <div class="row record-padding col-md-9">
-          <%= paginate array_of_ids, outer_window: 2, theme: 'blacklight', param_name: :page, route_set: main_app %>
+          <%= paginate presenter.list_of_item_ids_to_display, outer_window: 2, theme: 'blacklight', param_name: :page, route_set: main_app %>
         </div><!-- /pager -->
     <% end %>
   </div>

app/views/themes/cultural_show/hyrax/oers/_related_items.html.erb

@@ -21,7 +21,7 @@
   <div class="row">
     <% if presenter.total_pages > 1 %>
         <div class="row record-padding col-md-9">
-          <%= paginate array_of_ids, outer_window: 2, theme: 'blacklight', param_name: :page, route_set: main_app %>
+          <%= paginate presenter.list_of_item_ids_to_display, outer_window: 2, theme: 'blacklight', param_name: :page, route_set: main_app %>
         </div><!-- /pager -->
     <% end %>
   </div>