Switch to non-deprecated Extension class

Author: derrabus

src/DependencyInjection/FlysystemExtension.php

@@ -21,8 +21,8 @@
 use League\FlysystemBundle\Lazy\LazyFactory;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Extension\Extension;
 use Symfony\Component\DependencyInjection\Reference;
-use Symfony\Component\HttpKernel\DependencyInjection\Extension;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
 /**