Ticket #33511: 33511.patch

src/wp-includes/general-template.php

@@ -709 +709 @@
                         break;
                 case 'language':
                         $output = get_locale();
-                        $output = str_replace('_', '-', $output);
+                        $output = str_replace( '_', '-', $output );
+                        $output = str_replace( '-formal', '', $output );
                         break;
                 case 'text_direction':
                         _deprecated_argument( __FUNCTION__, '2.2', sprintf(