Add Aggregate Failures block

- To help diagnose a flaky feature spec

spec/support/features/discussion_comments_shared_example.rb

@@ -275,6 +275,7 @@ shared_examples 'thread comments' do |resource_name|
             find("#{menu_selector} li", match: :first)
             items = all("#{menu_selector} li")
 
+            aggregate_failures do
               expect(items.first).to have_content 'Comment'
               expect(items.first).to have_selector '.fa-check'
               expect(items.first['class']).to match 'droplab-item-selected'
@@ -287,6 +288,7 @@ shared_examples 'thread comments' do |resource_name|
         end
       end
     end
+  end
 
   if resource_name =~ /(issue|merge request)/
     describe "on a closed #{resource_name}" do