financial#151 Paypal express validation fix on event

extension of https://github.com/civicrm/civicrm-core/pull/18459

CRM/Core/Payment/PayPalImpl.php

@@ -1132,8 +1132,13 @@ class CRM_Core_Payment_PayPalImpl extends CRM_Core_Payment {
     // The contribution form passes a 'button' but the event form might still set one of these fields.
     // @todo more standardisation & get paypal fully out of the form layer.
     $possibleExpressFields = [
+      // @todo - we think these top 2 are likely not required & it's still here
+      // on a precautionary basis.
+      // see https://github.com/civicrm/civicrm-core/pull/18680
       '_qf_Register_upload_express_x',
       '_qf_Payment_upload_express_x',
+      '_qf_Register_upload_express',
+      '_qf_Payment_upload_express',
       '_qf_Main_upload_express',
     ];
     if (array_intersect_key($params, array_fill_keys($possibleExpressFields, 1))) {