cs: Enable risky rule static_lambda.

src/Bundle/ChillActivityBundle/DependencyInjection/Configuration.php

@@ -56,7 +56,7 @@ class Configuration implements ConfigurationInterface
             ->info('The number of seconds of this duration. Must be an integer.')
             ->cannotBeEmpty()
             ->validate()
-            ->ifTrue(function ($data) {
+            ->ifTrue(static function ($data) {
                 return !is_int($data);
             })->thenInvalid('The value %s is not a valid integer')
             ->end()