Update to the latest ruby module (8.0.3)

There are some breakages between this version and the previous one: 
https://github.com/boxen/puppet-ruby#breakages-since-last-major-version

We don't use `rbenv::plugin` or `chruby` and we already have the
`module-data` module, so those aren't problems. I've installed `bundler` for
all rubies, so that's dealt with.

The moving of rubies from `/opt/boxen/rbenv/versions` to `/opt/rubies` makes this
a bit of a warm update, as it's going to build new ruby versions. It's best to
get lunch or a coffee while boxen is running.