MAGETWO-65521: Remove unserialize in \Magento\Framework\DB\Adapter\Pdo\Mysql

- fixing annotation

Author: Igor Melnikov

lib/internal/Magento/Framework/Model/ResourceModel/Type/Db/Pdo/Mysql.php

@@ -57,8 +57,8 @@ public function getConnection(DB\LoggerInterface $logger = null, SelectFactory $
     /**
      * Create and return database connection object instance
      *
-     * @param DB\LoggerInterface $logger
-     * @param SelectFactory $selectFactory
+     * @param DB\LoggerInterface|null $logger
+     * @param SelectFactory|null $selectFactory
      * @return \Magento\Framework\DB\Adapter\Pdo\Mysql
      */
     protected function getDbConnectionInstance(DB\LoggerInterface $logger = null, SelectFactory $selectFactory = null)