Stop running Mkdocs JSON builder
Stop running Mkdocs JSON builder

This has been removed from mkdocs,
so we should stop running it.

It will fix the error here: http://readthedocs.org/projects/mkdocs/builds/6503359/

safwanrahman/readthedocs.org,rtfd/readthedocs.org,davidfischer/readthedocs.org,safwanrahman/readthedocs.org,davidfischer/readthedocs.org,rtfd/readthedocs.org,rtfd/readthedocs.org,safwanrahman/readthedocs.org,rtfd/readthedocs.org,davidfischer/readthedocs.org,davidfischer/readthedocs.org,safwanrahman/readthedocs.org