Added return types to normalize method.
Return types avoid this fatal error in Drupal 10:
PHP Fatal error: Declaration of Drupal\rest_absolute_urls\Normalizer\StringDataNormalizer::normalize($object, $format = null, array context = []) must be compatible with Drupal\serialization\Normalizer\PrimitiveDataNormalizer::normalize(
object, $format = null, array $context = []): ArrayObject|array|string|int|float|bool|null in /var/www/html/docroot/modules/contrib/rest_absolute_urls/src/Normalizer/StringDataNormalizer.php on line 40