chore: Add new mpdf version to upgrade guide

Author: mitelg

UPGRADE-5.7.md

@@ -30,7 +30,7 @@ This changelog references changes done in Shopware 5.7 patch versions.
 * Updated `guzzlehttp/guzzle` to version 7.9.2
 * Updated `guzzlehttp/psr7` to version 2.7.0
 * Updated `monolog/monolog` to version 2.10.0
-* Updated `mpdf/mpdf` to version 8.2.4
+* Updated `mpdf/mpdf` to version 8.2.5
 * Updated `laminas/laminas-code` to version 4.16.0 for PHP 8.1 and newer
 * Updated `laminas/laminas-escaper` to version 2.15.0 for PHP 8.1 and newer
 * Updated `phpunit/phpunit` to version 9.6.21