[DOCS] Removes X-Pack settings section

[lcawl]

Summary

This PR removes the "X-Pack Settings" section from the Kibana User Guide. Instead, those pages are moved under Set up Kibana > Configuring Kibana.

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

- [ ] This was checked for cross-browser compatibility, including a check against IE11
- [ ] Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

• Documentation was added for features that require explanation or tutorials
  - [ ] Unit or functional tests were updated or added to match the most common scenarios
  - [ ] This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

[skip ci]

[elasticmachine]

Pinging @elastic/kibana-docs

[lcawl]

Something to consider is whether you prefer that pages that just contain one or two settings (like the "Development tools settings" and "Graph settings", and "Machine learning settings" for example) be integrated into the main "Configuring Kibana" page instead (as was done for the rollup and license management settings).

In my opinion it's a good idea to leave them as-is so they can be linking to separately, but I'm open to other ideas.

[schersh]

Built locally, LGTM.

[schersh]

Something to consider is whether you prefer that pages that just contain one or two settings (like the "Development tools settings" and "Graph settings", and "Machine learning settings" for example) be integrated into the main "Configuring Kibana" page instead (as was done for the rollup and license management settings).

In my opinion it's a good idea to leave them as-is so they can be linking to separately, but I'm open to other ideas.

I would agree that it's helpful to have those settings as separate pages. The main Configuring Kibana page might be helped by subsections or some kind of linked TOC? There's a lot of info there.