Use doctrine entity to truncate table in tests

[MAILPOET-3027]

tests/integration/Cron/Workers/SendingQueue/Tasks/PostsTest.php

@@ -3,9 +3,8 @@
 namespace MailPoet\Test\Cron\Workers\SendingQueue\Tasks;
 
 use MailPoet\Cron\Workers\SendingQueue\Tasks\Posts as PostsTask;
+use MailPoet\Entities\NewsletterPostEntity;
 use MailPoet\Models\Newsletter;
-use MailPoet\Models\NewsletterPost;
-use MailPoetVendor\Idiorm\ORM;
 
 class PostsTest extends \MailPoetTest {
 
@@ -61,6 +60,6 @@ class PostsTest extends \MailPoetTest {
   }
 
   public function _after() {
-    ORM::raw_execute('TRUNCATE ' . NewsletterPost::$_table);
+    $this->truncateEntity(NewsletterPostEntity::class);
   }
 }