fix(graphql): increment graphql normalizer priority

closes #6279 #6264

Author: soyuka

src/Symfony/Bundle/Resources/config/graphql.xml

@@ -213,8 +213,8 @@
             <argument type="service" id="api_platform.metadata.resource.metadata_collection_factory" on-invalid="ignore" />
             <argument type="service" id="api_platform.security.resource_access_checker" on-invalid="ignore" />
 
-            <!-- Run before serializer.normalizer.json_serializable -->
-            <tag name="serializer.normalizer" priority="-890" />
+            <!-- Run before serializer.normalizer.json_serializable and before serializer.normalizer.backed_enum which is at 880 -->
+            <tag name="serializer.normalizer" priority="-878" />
         </service>
 
         <service id="api_platform.graphql.normalizer.object" class="ApiPlatform\GraphQl\Serializer\ObjectNormalizer" public="false">