Use question icon to link to docs

app/views/admin/application_settings/_form.html.haml

@@ -100,12 +100,13 @@
       .col-sm-10
         = f.number_field :max_attachment_size, class: 'form-control'
     .form-group
-      = f.label :repository_size_limit, 'Size limit per repository (MB)', class: 'control-label col-sm-2'
+      = f.label :repository_size_limit, class: 'control-label col-sm-2' do
+        Size limit per repository (MB)
       .col-sm-10
         = f.number_field :repository_size_limit, class: 'form-control', min: 0
         %span.help-block#repository_size_limit_help_block
           Includes LFS objects. It can be overridden per group, or per project. 0 for unlimited.
-          = link_to "(?)", help_page_path("user/admin_area/settings/account_and_limit_settings")
+          = link_to icon('question-circle'), help_page_path("user/admin_area/settings/account_and_limit_settings")
     .form-group
       = f.label :session_expire_delay, 'Session duration (minutes)', class: 'control-label col-sm-2'
       .col-sm-10