Add missing application_setting option

app/models/ee/application_setting.rb

 module EE
-  # Build EE mixin
+  # ApplicationSetting EE mixin
   #
   # This module is intended to encapsulate EE-specific model logic
-  # and be included in the `Build` model
-  module Build
-    extend ActiveSupport::Concern
+  # and be included in the `ApplicationSetting` model
+  module ApplicationSetting
+    extend ActiveSupport::Prependable
 
-    def shared_runners_minutes_limit_enabled?
-      runner && runner.shared? && project.shared_runners_minutes_limit_enabled?
+    prepended do
+      validates :shared_runners_minutes,
+                numericality: { greater_than_or_equal_to: 0 }
     end
   end
 end