Remove def favicon from extended status

lib/gitlab/ci/status/build/failed_allowed.rb

@@ -13,10 +13,6 @@ module Gitlab
             'icon_status_warning'
           end
 
-          def favicon
-            'favicon_status_warning'
-          end
-
           def group
             'failed_with_warnings'
           end

lib/gitlab/ci/status/success_warning.rb

@@ -20,10 +20,6 @@ module Gitlab
           'icon_status_warning'
         end
         
-        def favicon
-          'favicon_status_warning'
-        end
-        
         def group
           'success_with_warnings'
         end