[8.6] Documents how to change the default security index (backport #4695)

[mergify]

This is an automatic backport of pull request #4695 done by Mergify.
Cherry-pick of 225f3c8 has failed:

On branch mergify/bp/8.6/pr-4695
Your branch is up to date with 'origin/8.6'.

You are currently cherry-picking commit 225f3c8d.
  (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/getting-started/data-views-in-sec.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

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