Fix sandbox variable, thanks in advance

Please fix this, it’s 1 row.

I have large amount of error logs just with this

[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuCreditCard::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuListBanks::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuStandard::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuSecureForm::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuBlik::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuInstallments::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuKlarna::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuPaypo::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42
[10-May-2024 14:24:30 UTC] PHP Deprecated:  Creation of dynamic property WC_Gateway_PayuTwistoPl::$sandbox is deprecated in /code-project/wp-content/plugins/woo-payu-payment-gateway/includes/WC_PayUGateways.php on line 42