handlePaymentNotification should not be static

CRM/Core/Payment/Stripe.php

@@ -1130,7 +1130,7 @@ class CRM_Core_Payment_Stripe extends CRM_Core_Payment {
    * @throws \CiviCRM_API3_Exception
    * @throws \Stripe\Error\Api
    */
-  public static function handlePaymentNotification() {
+  public function handlePaymentNotification() {
     $data_raw = file_get_contents("php://input");
     $data = json_decode($data_raw);
     $ipnClass = new CRM_Core_Payment_StripeIPN($data);