[DI] fix CS

Author: nicolas-grekas

Tests/Dumper/PhpDumperTest.php

@@ -18,7 +18,6 @@
 use Symfony\Component\DependencyInjection\Argument\IteratorArgument;
 use Symfony\Component\DependencyInjection\Argument\RewindableGenerator;
 use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
-use Symfony\Component\DependencyInjection\ChildDefinition;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface as SymfonyContainerInterface;
 use Symfony\Component\DependencyInjection\Dumper\PhpDumper;