Use the proxy listener instead of the route

Needed after the recent changes: cf https://github.com/symfony/symfony/commit/ad8289369128fc1e72f9f8f11b738679ed35a6de and https://github.com/fabpot/symfony-docs/commit/7ab8be5a9c8e9f36eedf0b3dd3b815f23b159c1f