use adyen helper to create adyen checkout service (#789)

This is just so we can use a plugin on `createAdyenCheckoutService` class, which we currently cannot do because of `new`.
Co-authored-by: Attila Kiss <42297201+cyattilakiss@users.noreply.github.com>

Gateway/Http/Client/TransactionPayment.php

@@ -68,8 +68,7 @@ class TransactionPayment implements ClientInterface
         }
 
         $client = $this->adyenHelper->initializeAdyenClient();
-
-        $service = new \Adyen\Service\Checkout($client);
+        $service = $this->adyenHelper->createAdyenCheckoutService($client);
 
         $requestOptions = [];