Rename v5 FontAwesome icons to match v6 name

While FontAwesome provides aliases for all icons, we switch to the new names for consistency. See all changes at:
https://fontawesome.com/docs/web/setup/upgrade/whats-changed#icons-renamed-in-version-6

spec/helpers/application_helper_spec.rb

@@ -39,7 +39,7 @@ describe ApplicationHelper do
 
   describe '#no' do
     it "builds an 'i' tag" do
-      expect(no).to have_css('i.fa.fa-times')
+      expect(no).to have_css('i.fa.fa-xmark')
     end
   end