[DI] Update code examples to use tagged_iterator

Author: jschaedl

service_container/tags.rst

@@ -474,7 +474,7 @@ first  constructor argument to the ``App\HandlerCollection`` service:
 
             App\HandlerCollection:
                 # inject all services tagged with app.handler as first argument
-                arguments: [!tagged app.handler]
+                arguments: [!tagged_iterator app.handler]
 
     .. code-block:: xml
 
@@ -496,7 +496,7 @@ first  constructor argument to the ``App\HandlerCollection`` service:
 
                 <service id="App\HandlerCollection">
                     <!-- inject all services tagged with app.handler as first argument -->
-                    <argument type="tagged" tag="app.handler"/>
+                    <argument type="tagged_iterator" tag="app.handler"/>
                 </service>
             </services>
         </container>