Update service_container/tags.rst

Co-Authored-By: XuruDragon <[email protected]>

Author: OskarStark

service_container/tags.rst

@@ -636,7 +636,7 @@ but we can now access a specific injected service:
             ->addArgument(new TaggedIteratorArgument('app.handler', 'key'));
 
 After compilation the ``HandlerCollection`` is able to iterate over your
-application handlers. But we want to retrieve a specific service by it's
+application handlers. To retrieve a specific service by it's ``key`` attribute
 ``key`` attribute. As it's an iterator, we can use ``iterator_to_array``
 to get an array and then retrieve the ``handler_two`` handler :