fix: migrate ORDER_NR placeholder to ORDER_ID in label descriptions

Add transformation in PdkSettingsMigration to replace [ORDER_NR] with
[ORDER_ID] during settings migration to maintain consistency with
WooCommerce implementation and ensure the placeholder works correctly.

Author: NabDevs

src/Migration/Pdk/PdkSettingsMigration.php

@@ -374,6 +374,7 @@ private function getSettingsTransformationMap(): Generator
                 return strtr((string) $value, [
                     '{order.id}'        => '[ORDER_ID]',
                     '{order.reference}' => '[ORDER_ID]',
+                    '[ORDER_NR]'        => '[ORDER_ID]',
                 ]);
             })
         );