Add known issue for AWS S3 input (target main)

[kilfoyle]

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

Closes: https://github.com/elastic/ingest-docs/issues/1491 Rel: https://github.com/elastic/beats/pull/41735 (same change targeting 8.16) Rel: https://github.com/elastic/beats/pull/41733 (same change targeting 8.15)

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[mergify[bot]]

This pull request does not have a backport label. If this is a bug or security fix, could you label this PR @kilfoyle? 🙏. For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify[bot]]

backport-8.x has been added to help with the transition to the new branch 8.x. If you don't need it please use backport-skip label and remove the backport-8.x label.

[pierrehilbert]

Should we remove the 8.17 backport label?

No we should keep it as we need to have this changelog updated on all branches