Update readthedocs/api/v2/serializers.py
Update readthedocs/api/v2/serializers.py

Co-authored-by: Manuel Kaufmann <54d769c38f2aa6d2679b577ce2986fc3d1abeaba@gmail.com>
rtfd/readthedocs.org,rtfd/readthedocs.org,rtfd/readthedocs.org,rtfd/readthedocs.org