Fixed typo

Author: Tiago Ribeiro

Resources/doc/the_oauth_event_class.md

@@ -58,7 +58,7 @@ The `$user` variable has a method `isAuthorizedClient()` which contains your log
 the given client (`ClientInterface`) is allowed by the user, or not. This `$user` is part of your
 own model layer, and loaded using the `username` property (see `getUser()`).
 
-### Registring the listener
+### Registering the listener
 
 ``` yaml
 services: