Fixed s3 sink config validation

[kkondaka]

Description

Fixed s3 sink config validation

Issues Resolved

Resolves #[Issue number to be closed when this PR is merged]

Check List

• [ X] New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
• [X ] Commits are signed with a real name per the DCO

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[opensearch-trigger-bot]

The backport to 2.10 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.10 2.10
# Navigate to the new working tree
cd .worktrees/backport-2.10
# Create a new branch
git switch --create backport/backport-5063-to-2.10
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 47fdbda0f7fff077f8725f00f2eb42a8f07816d2
# Push it to GitHub
git push --set-upstream origin backport/backport-5063-to-2.10
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.10

Then, create a pull request where the base branch is 2.10 and the compare/head branch is backport/backport-5063-to-2.10.