Change k-NN Faiss example method to IVF

[kolchfa-aws]

Change k-NN Faiss example method to IVF

Checklist

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[naveentatikonda]

Looks good. Thanks @kolchfa-aws

[natebower]

LGTM

[opensearch-trigger-bot]

The backport to 2.9 failed:

The process '/usr/bin/git' failed with exit code 128

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-2.9 2.9
# Navigate to the new working tree
pushd ../.worktrees/backport-2.9
# Create a new branch
git switch --create backport/backport-5320-to-2.9
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 238109a29a6ac9a1bc437e4ff480c339ec0c2d83
# Push it to GitHub
git push --set-upstream origin backport/backport-5320-to-2.9
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.9

Then, create a pull request where the base branch is 2.9 and the compare/head branch is backport/backport-5320-to-2.9.