Apply various updates and add reminder for collapse

app/views/exercises/_file_form.html.slim

@@ -11,7 +11,8 @@ li.card.mt-2
           span = f.object.name_with_extension
         - else
           span = f.object.name
-  .card-collapse.collapse class=('in' if f.object.name.nil?) id="collapse#{f.index}" role="tabpanel"
+  // FIXME: Re-add .collapse
+  .card-collapse class=('in' if f.object.name.nil?) id="collapse#{f.index}" role="tabpanel"
     .card-body
       - if policy(f.object).destroy? && id.present?
         .clearfix

app/views/exercises/show.html.slim

@@ -36,7 +36,8 @@ ul.list-unstyled#files
           div.clearfix role="button"
             i class="fa" aria-hidden="true"
             span = file.name_with_extension
-      .card-collapse.collapse class="collapse#{file.id}" role="tabpanel"
+      // FIXME: Re-add .collapse
+      .card-collapse class="collapse#{file.id}" role="tabpanel"
         .card-body
           - if policy(file).destroy?
             .clearfix = link_to(t('shared.destroy'), file, class:'btn btn-warning btn-sm float-right', data: {confirm: t('shared.confirm_destroy')}, method: :delete)