[8.10](backport #3716) Clarify AI Assistant docs about model training

[mergify]

Change requested by @grabowskit in slack.

After merging:

• Port this change to serverless.

@grabowskit Let me know which releases you want this backported to.

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This is an automatic backport of pull request #3716 done by Mergify.

[mergify]

Cherry-pick of 479f34f has failed:

On branch mergify/bp/8.10/pr-3716
Your branch is up to date with 'origin/8.10'.

You are currently cherry-picking commit 479f34ff.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/en/observability/observability-ai-assistant.asciidoc

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

A documentation preview will be available soon:

• 📚 HTML diff
• 📙 Observability Guide