Auto devops docs improvements

What does this MR do?

Remove confusing mention of gitlab helm chart in auto devops docs:

This does not actually make it any easier to use Auto DevOps so these docs are not helpful as you still need to do all the same configuration regardless if your GitLab instance is itself running on Kubernetes. This TIP may serve to confuse people more than help as they assume there is some connection between running gitlab on Kubernetes and Auto DevOps.

Remove mention of wildcard TLS and kube-lego from auto devops docs

There are many reasons for removing this:

1. kube-lego is not really being actively maintained anymore and is being superseded by cert-manager
2. kube-lego is not intended for production usage anyway
3. these instructions are not helpful as there are missing steps after just installing kube-lego (eg. updating the auto-deploy-app to actually use TLS routes for your app)
4. If you are installing cluster apps through GitLab UI we add TLS mutual auth to tiller so this makes it diffult (sometimes impossible) to actually install custom helm applications outside of the ones we support through our UI anyway

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• [-] Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [-] Conforms to the database guides