[8.x] Update "Download and deploy ELSER" snippet with adaptive allocations (backport #2878)

[mergify]

Does what it says on tin

cc @linyaru

---

This is an automatic backport of pull request #2878 done by Mergify.

[mergify]

Cherry-pick of 5740148 has failed:

On branch mergify/bp/8.x/pr-2878
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 57401489.
  (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/stack/ml/nlp/ml-nlp-elser.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]

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[mergify]

This pull request has not been merged yet. Could you please review and merge it @leemthompo? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @leemthompo? 🙏

[szabosteve]

@elasticsearchmachine update branch