Update verbatim tag hyperlink

[B3QL]

Django 1.5 documentation isn't available so current hyperlink points to 404 error page.

[adrienbrunet]

Thanks!

[jrief]

Thanks @B3QL Presumingly the most future proof way for linking to the Django docs, is to use the stable tag, say https://docs.djangoproject.com/en/stable/ref/templates/builtins/#verbatim

[adrienbrunet]

I just updated the docs to use '/stable/' instead of 1.5 and 1.9 =)