Tweak to many_to_one_null doctest to avoid primary key assumptions (causing breakage on PostgreSQL).
Tweak to many_to_one_null doctest to avoid primary key assumptions (causing breakage on PostgreSQL).

git-svn-id: 4f9f921b081c523744c7bf24d959a0db39629563@14168 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Instagram/django,alex/django-old,disqus/django-old,mitsuhiko/django,Instagram/django,django-nonrel/django-nonrel,skevy/django,jamespacileo/django-france,mitsuhiko/django,django-nonrel/django-nonrel,jamespacileo/django-france,django-nonrel/django-nonrel,Instagram/django,alex/django-old,jamespacileo/django-france,alex/django-old,mitsuhiko/django,skevy/django,disqus/django-old,skevy/django,disqus/django-old