Fixed checkstyle

Author: yann-eugone

src/batch/tests/Job/Item/Writer/Filesystem/JsonLinesWriterTest.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Yokai\Batch\Tests\Job\Item\Writer\Filesystem;
 
 use PHPUnit\Framework\TestCase;