docs : update autowiring.rst

Add missing `arguments` key in `services.yaml` code block example - `#dealing-with-multiple-implementations-of-the-same-type` section.

Author: bsureau

service_container/autowiring.rst

@@ -464,6 +464,7 @@ the injection::
 
                 # If you wanted to choose the non-default service and do not
                 # want to use a named autowiring alias, wire it manually:
+                # arguments:
                 #     $transformer: '@App\Util\UppercaseTransformer'
                 # ...