Use a labeled <aside> for tools sidebar

This mirrors template changes in Blacklight 8.8 that convert the
sidebar from a <section> into an <aside> with label.

Ref projectblacklight/blacklight@2fa70cf

Closes #1437

app/views/layouts/catalog_result.html.erb

@@ -2,9 +2,9 @@
 <%= render Blacklight::Document::PageHeaderComponent.new(document: @document, search_context: @search_context, search_session: search_session) %>
 <% end %>
 <% content_for(:content) do %>
-  <section class="<%= show_sidebar_classes %>">
+  <aside class="<%= show_sidebar_classes %>" aria-label="<%= t('.aria.sidebar') %>">
     <%= content_for(:sidebar) %>
-  </section>
+  </aside>
 
   <section class="<%= show_content_classes %>">
     <%= yield %>