Make code block consistent in serialization tutorial
Make code block consistent in serialization tutorial

All the other code blocks in the Serialization tutorial can be copied and pasted, but there is one that includes the >>> shell prompt characters. This commit removes those characters, and also makes the output consistent with other code blocks by making it a comment.
agconti/django-rest-framework,ossanna16/django-rest-framework,werthen/django-rest-framework,davesque/django-rest-framework,uploadcare/django-rest-framework,sheppard/django-rest-framework,jpadilla/django-rest-framework,edx/django-rest-framework,dmwyatt/django-rest-framework,dmwyatt/django-rest-framework,callorico/django-rest-framework,kgeorgy/django-rest-framework,sheppard/django-rest-framework,werthen/django-rest-framework,agconti/django-rest-framework,atombrella/django-rest-framework,johnraz/django-rest-framework,linovia/django-rest-framework,pombredanne/django-rest-framework,kgeorgy/django-rest-framework,uploadcare/django-rest-framework,linovia/django-rest-framework,uploadcare/django-rest-framework,dmwyatt/django-rest-framework,linovia/django-rest-framework,davesque/django-rest-framework,atombrella/django-rest-framework,pombredanne/django-rest-framework,atombrella/django-rest-framework,agconti/django-rest-framework,tomchristie/django-rest-framework,ossanna16/django-rest-framework,jpadilla/django-rest-framework,tomchristie/django-rest-framework,jpadilla/django-rest-framework,johnraz/django-rest-framework,johnraz/django-rest-framework,rhblind/django-rest-framework,tomchristie/django-rest-framework,davesque/django-rest-framework,rhblind/django-rest-framework,ossanna16/django-rest-framework,callorico/django-rest-framework,sheppard/django-rest-framework,pombredanne/django-rest-framework,rhblind/django-rest-framework,edx/django-rest-framework,callorico/django-rest-framework,werthen/django-rest-framework,edx/django-rest-framework,kgeorgy/django-rest-framework