fixes #8491 - removing puppet modules list from content view version api

This takes the CVV index api from ~5 minutes down to 17 seconds
for 47 content view versions, 10 having 100 puppet modules, the rest having
5
I think it means that he can't extend `_metadata.json.rabl` in the index layout. That means he either has to:

1. Have content_view_versions/index.json.rabl extend `_metadata.json.rabl`.
2. Not use `_metadata.json.rabl` and keep this PR the way it is.

I'm in favor of 2 because it's what foreman does and also `_metadata.json.rabl` will go away when we switch over to 2 for our other index actions.