Update MenuLink.php

Currently if on php 8.1 and the latest version of SS - Line 370 in /app/vendor/symbiote/silverstripe-gridfieldextensions/src/GridFieldOrderableRows.php throws an error as the sort is expected to be a string.  Setting to a default convention which will work.  See - symbiote/silverstripe-gridfieldextensions#344 for more details

src/models/MenuLink.php

@@ -83,7 +83,7 @@ class MenuLink extends Link
      * Default sort ordering
      * @var array
      */
-    private static $default_sort = ['Sort' => 'ASC'];
+    private static $default_sort = 'Sort ASC';
 
     /**
      * CMS Fields