The function getFilterParameters is marked as final since Sonata 4.0.0. You need to use the configureDefaultFilterValues function

protected function configureDefaultFilterValues(array &$filterValues): void
{
    $filterValues['assignee'] = 
        [
            'value' => $this->getUser()->getId(),
        ];
}

Source : https://github.com/sonata-project/SonataAdminBundle/blob/4.0.0/src/Admin/AbstractAdmin.php