Revert "Add chef-redis recipe"

This reverts commit bdb1677399999a1a8c61ae5b77fcece9db17d832.

Forgot to add the cookbooks folder to the Vagrantfile and referenced an
empty recipe.

But also, the recipe we want to use assumes a too recent version of
Redis. The configuration file it generates can't be understood by the
version available on our source Vagrant box.