Remove asciidoc index tag
Remove asciidoc index tag

Sphnix creates an index implicitly at the bottom of the page so an
explicitly index creation is not required.

Possible issues:

* The index is at the bottom of the page; it used to be at the top.
* The index is not numbered, neither are the sections.

djangonauts/django-hstore,djangonauts/django-hstore,djangonauts/django-hstore,djangonauts/django-hstore