Fix MongoDB test

Author: GromNaN

tests/DependencyInjection/MonologExtensionTest.php

@@ -1058,7 +1058,6 @@ public function testMongoDB()
 
         // A MongoDBFormatter will be applied to each handler by default
         $formatter = new Definition('Monolog\Formatter\MongoDBFormatter');
-        $formatter->setPublic(false);
 
         // MongoDB handler should receive the mongodb.client as first argument
         $handler = $container->getDefinition('monolog.handler.mongodb_with_id');