Use annotation to ignore phpstan rule (#512)

* Use annotation to ignore phpstan rule

* Replace assert by comment

Author: jderusse

src/DependencyInjection/Configuration.php

@@ -16,6 +16,7 @@ public function getConfigTreeBuilder()
         $treeBuilder = new TreeBuilder('async_aws');
         /** @var ArrayNodeDefinition $rootNode */
         $rootNode = $treeBuilder->getRootNode();
+        /** @phpstan-ignore-next-line */
         $rootNode
             ->fixXmlConfig('client')
             ->children()