[8.x](backport #41734) Add known issue for AWS S3 input (target main)

[mergify]

Adds a known issue to the 8.16 and 8.15 release notes for the AWS S3 input.

Closes: elastic/ingest-docs#1491
Rel: #41735 (same change targeting 8.16)
Rel: #41733 (same change targeting 8.15)

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This is an automatic backport of pull request #41734 done by Mergify.

[mergify]

Cherry-pick of bb9968a has failed:

On branch mergify/bp/8.x/pr-41734
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit bb9968a0f8.
  (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:   CHANGELOG.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

[botelastic]

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