Merge branch 'make_spec_admin_sends_notification_spec_reliable' into 'master'

Make ee/spec/features/admin/admin_sends_notification_spec.rb more reliable

See merge request gitlab-org/gitlab-ee!5547

ee/spec/features/admin/admin_sends_notification_spec.rb

@@ -12,6 +12,8 @@ describe "Admin sends notification", :js do
     sign_in(admin)
 
     visit(admin_email_path)
+
+    ActionMailer::Base.deliveries.clear
   end
 
   it "sends notification" do