Migrate fa-spinner to spinner in milestones directory

app/views/shared/milestones/_delete_button.html.haml

@@ -9,6 +9,6 @@
   milestone_merge_request_count: @milestone.merge_requests.count },
   disabled: true }
   = _('Delete')
-  = icon('spin spinner', class: 'js-loading-icon hidden' )
+  .spinner.js-loading-icon.hidden
 
 #delete-milestone-modal

app/views/shared/milestones/_sidebar.html.haml

@@ -98,10 +98,6 @@
         human_time_estimate: @milestone.human_total_issue_time_estimate,
         human_time_spent: @milestone.human_total_issue_time_spent,
         limit_to_hours: Gitlab::CurrentSettings.time_tracking_limit_to_hours.to_s } }
-        // Fallback while content is loading
-        .title.hide-collapsed
-          = _('Time tracking')
-          = icon('spinner spin')
 
     = render_if_exists 'shared/milestones/weight', milestone: milestone
 

app/views/shared/milestones/_tab_loading.html.haml

 .text-center.prepend-top-default
-  = icon('spin spinner 2x', 'aria-hidden': 'true', 'aria-label': 'Loading tab content')
+  .spinner.spinner-md