Revert "MDL-43306 restore: fix grade item sortorder restoration"

This reverts commit 6afd79df8d.

backup/moodle2/restore_stepslib.php

@@ -2782,9 +2782,9 @@ class restore_activity_grades_structure_step extends restore_structure_step {
         $gradeitem = new grade_item($data, false);
         $gradeitem->insert('restore');
 
-        // Reinstate the grade item close to its original sortorder, if something already exists
-        // in the original sortorer then it will be first.
-        $gradeitem->move_after_sortorder($data->sortorder);
+        //sortorder is automatically assigned when inserting. Re-instate the previous sortorder
+        $gradeitem->sortorder = $data->sortorder;
+        $gradeitem->update('restore');
 
         // Set mapping, saving the original category id into parentitemid
         // gradebook restore (final task) will need it to reorganise items