[8.x](backport #4646) add logs explorer note to settings page

[mergify]

Description

These logs settings only apply to the Logs Stream app, which will be deprecated in an upcoming release.
This PR adds a note that recommends people use Logs Explorer.

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• None of the above

Related issue

Closes #4540

Checklist

• Product/Engineering Review
• Writer Review

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)

---

This is an automatic backport of pull request #4646 done by [Mergify](https://mergify.com).

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