fix: PHP 8 compatibility warnings and fatal errors

Agent-Logs-Url: https://github.com/GameServerPanel/GSP/sessions/5ac91d14-7688-4ab2-9065-10d4a361750f

Co-authored-by: iaretechnician <2749183+iaretechnician@users.noreply.github.com>

modules/user_games/billing_integration.php

@@ -134,7 +134,6 @@ if (!function_exists('admin_register_server_in_billing')) {
             'payment_txid'             => 'admin-created',
             'paid_ts'                  => $now,
             'coupon_id'                => 0,
-            'extended'                 => 0,
         );
 
         $order_id = $db->resultInsertId('billing_orders', $order_fields);