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

app/views/exercises/external_users/statistics.html.slim

@@ -43,12 +43,12 @@ h1
     .bg-light.w-100.p-2.mb-4.align-items-center.d-flex.justify-content-between
       - if @show_autosaves
         span.pl-1.pb-1
-          i.fa.fa-info-circle.align-middle
+          i.fa.fa-circle-info.align-middle
           small.mr-5.ml-1 = t('.toggle_status_on')
         = link_to t('.toggle_autosave_off'), statistics_external_user_exercise_path(show_autosaves: false), class: "btn btn-outline-dark float-right btn-sm"
       - else
         span.pl-1.pb-1
-          i.fa.fa-info-circle.align-middle
+          i.fa.fa-circle-info.align-middle
           small.mr-5.ml-1 = t('.toggle_status_off')
         = link_to t('.toggle_autosave_on'), statistics_external_user_exercise_path(show_autosaves: true), class: "btn btn-outline-dark float-right btn-sm"
   #timeline