change root location Id is not out of the box.
In the pagelayout.html.twig of the demoBundle, render function for the menu is called with a hard code location Id (location_id:2).
So, if we change it in a yml file, it won't have any effect.
We might use config Resolver to get root location Id of the current siteaccess instead :

$resolver = $this->container->get( 'ezpublish.config.resolver' );
$locationId = $resolver->getParameter( 'content.tree_root.location_id' );