ENGCOM-2233: [2.1-develop][BackPort] Fixed backwards incompatible change to Transport variable event parameters #16601

 - Merge Pull Request #16601 from gwharton/magento2:2.1-develop-10210
 - Merged commits:
   1. 390fc2f

Author: magento-engcom-team

app/code/Magento/Sales/Model/Order/Email/Sender/OrderSender.php

@@ -135,7 +135,7 @@ protected function prepareTemplate(Order $order)
          */
         $this->eventManager->dispatch(
             'email_order_set_template_vars_before',
-            ['sender' => $this, 'transport' => $transportObject->getData(), 'transportObject' => $transportObject]
+            ['sender' => $this, 'transport' => $transportObject, 'transportObject' => $transportObject]
         );
 
         $this->templateContainer->setTemplateVars($transportObject->getData());