[Serializer] update doc for 3.4 about normalizer

Author: lyrixx

serializer/custom_normalizer.rst

@@ -53,45 +53,15 @@ to customize the normalized data. To do that, leverage the ``ObjectNormalizer``:
         }
     }
 
-Registering it in Your Application
-----------------------------------
 
-In order to enable the normalizer in an application based on the entire Symfony
-framework, you must register it as a service and :doc:`tag it </service_container/tags>`
-with ``serializer.normalizer``.
+Registering it in your app
+--------------------------
 
-.. configuration-block::
+If you use the Symfony Framework. then you probably want to register this normalizer
+as a service in your app. If you're using the :ref:`default services.yml configuration <service-container-services-load-example>`,
+that's done automatically!
 
-    .. code-block:: yaml
+.. tip::
 
-        # app/config/services.yml
-        services:
-            app.yaml_encoder:
-                class: AppBundle\Serializer\TopicNormalizer
-                tags:
-                    - { name: serializer.normalizer }
-
-    .. code-block:: xml
-
-        <!-- app/config/services.xml -->
-        <?xml version="1.0" encoding="UTF-8" ?>
-        <container xmlns="http://symfony.com/schema/dic/services"
-            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-            xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
-
-            <services>
-                <service id="app.yaml_encoder" class="AppBundle\Serializer\TopicNormalizer">
-                    <tag name="serializer.normalizer" />
-                </service>
-            </services>
-        </container>
-
-    .. code-block:: php
-
-        // app/config/services.php
-        use AppBundle\Serializer\TopicNormalizer;
-
-        $container
-            ->register('app.yaml_encoder', TopicNormalizer::class)
-            ->addTag('serializer.normalizer')
-        ;
+    If you're not using autoconfigure, make sure to register your class as a service
+    and tag it with ``serializer.normalizer``.