[1.8.x] Corrected some inconsistent headings in docs/ref/templates/builtins.txt.
[1.8.x] Corrected some inconsistent headings in docs/ref/templates/builtins.txt.

Backport of 7080cef7bf12c7985d6c81822296e70d13553ef4 from master

h4r5h1t/django-hauthy,h4r5h1t/django-hauthy,h4r5h1t/django-hauthy,h4r5h1t/django-hauthy