Update composer package doctrine/dbal

We cannot update to the latest version of the dbal 3 because there is a another package conflict.
[MAILPOET-6101]

mailpoet/tests/integration/API/JSON/v1/ImportExportTest.php

@@ -25,7 +25,7 @@ class ImportExportTest extends \MailPoetTest {
     $this->entityManager->createQueryBuilder()
       ->delete(ScheduledTaskEntity::class, 's')
       ->where('s.type = :type')
-      ->setParameter(':type', WooCommerceSync::TASK_TYPE)
+      ->setParameter('type', WooCommerceSync::TASK_TYPE)
       ->getQuery()
       ->execute();
   }