Removed button styling from restricted visibility levels and added checkboxes with icons

Review changes

app/helpers/application_settings_helper.rb

@@ -50,14 +50,14 @@ module ApplicationSettingsHelper
   def restricted_level_checkboxes(help_block_id)
     Gitlab::VisibilityLevel.options.map do |name, level|
       checked = restricted_visibility_levels(true).include?(level)
-      css_class = 'btn'
-      css_class += ' active' if checked
-      checkbox_name = 'application_setting[restricted_visibility_levels][]'
+      css_class = checked ? 'active' : ''
+      checkbox_name = "application_setting[restricted_visibility_levels][]"
 
-      label_tag(checkbox_name, class: css_class) do
+      label_tag(name, class: css_class) do
         check_box_tag(checkbox_name, level, checked,
                       autocomplete: 'off',
-                      'aria-describedby' => help_block_id) + name
+                      'aria-describedby' => help_block_id,
+                      id: name) + visibility_level_icon(level) + name
       end
     end
   end

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

@@ -22,9 +22,8 @@
     .form-group
       = f.label :restricted_visibility_levels, class: 'control-label col-sm-2'
       .col-sm-10
-        - data_attrs = { toggle: 'buttons' }
-        .btn-group{ data: data_attrs }
         - restricted_level_checkboxes('restricted-visibility-help').each do |level|
+          .checkbox
             = level
         %span.help-block#restricted-visibility-help
           Selected levels cannot be used by non-admin users for projects or snippets.

changelogs/unreleased/18136-ui-for-restricting-global-visibility-levels-is-unclear.yml

+---
+title: Changed restricted visibility admin buttons to checkboxes
+merge_request: 7463
+author: