[Suggestion]: Config managers overhaul

### Page URL

https://documentation.ubuntu.com/server/explanation/software/config-managers/

### Select an option

- [ ] I found what I was looking for
- [ ] I couldn't find what I was looking for
- [ ] I found the information, but it was incorrect
- [x] I found the information, but it was incomplete
- [ ] I found the information, but it was confusing
- [ ] I encountered a technical issue (e.g., broken link, image not loading)

### Issue Description

This page is less useful than it could be. Chef is no longer available in Ubuntu and should be removed.

To make it more useful, it could mention alternatives? Also, future, extend it to infrastructure (terraform) and service deployment (juju)? should this be an actual explanation page, or should it be moved to 'references'?

Start with the config-managers page at https://documentation.ubuntu.com/server/explanation/software/config-managers/. Confirm whether Chef should be removed, then define the scope for alternatives, Terraform and Juju coverage, and whether the content belongs in explanations or references; done means the page structure and content direction are resolved.

Written by the indexing model from the issue text.