[RoutingAutoBundle] Fix "typo" in YAML example

All the other examples (XML and PHP) use `cmf_routing_auto.not_exists_action` so I guess it's just a copy-paste error...

Author: lemoinem

bundles/routing_auto/customization.rst

@@ -117,7 +117,7 @@ It is registered in the DI configuration as follows:
                 class: Symfony\Cmf\Bundle\RoutingAutoBundle\RoutingAuto\PathNotExists\ThrowException
                 scope: prototype
                 tags:
-                    - { name: cmf_routing_auto.provider, alias: "throw_exception"}
+                    - { name: cmf_routing_auto.not_exists_action, alias: "throw_exception"}
 
     .. code-block:: xml