Update service_container/tags.rst

Co-Authored-By: XuruDragon <xurudragon@gmail.com>

Author: deguif

service_container/tags.rst

@@ -615,7 +615,7 @@ but we can now access to a specific injected service :
 
                 <service id="App\HandlerCollection">
                     <!-- inject all services tagged with app.handler as first argument -->
-                    <argument type="tagged" tag="app.handler" index-by="index_attribute_name"/>
+                    <argument type="tagged" tag="app.handler" index-by="index_attribute_name" />
                 </service>
             </services>
         </container>