Update spotless to meet JDK-21 baseline

[reta]

Is your feature request related to a problem? Please provide an existing Issue # , or describe. Update spotless to meet JDK-21 baseline

Describe the solution you are proposing A clear and concise description of what you want to happen.

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.

Check List

• [x] Backport Labels added.
• [x] New functionality includes testing.
  • [ ] All tests pass
• [x] New functionality has been documented.
  • [ ] New functionality has javadoc added
• [x] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[reta]

@ansjcy purely formatting changes (spotless update)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (bfab315) 69.40% compared to head (732f236) 69.32%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #618 +/- ## ============================================ - Coverage 69.40% 69.32% -0.08% + Complexity 372 371 -1 ============================================ Files 44 44 Lines 2706 2706 Branches 172 172 ============================================ - Hits 1878 1876 -2 - Misses 725 727 +2 Partials 103 103 ```

:umbrella: View full report in Codecov by Sentry.
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[reta]

@ansjcy @getsaurabh02 mind please taking a look folks? (last touches)

[opensearch-trigger-bot[bot]]

The backport to 2.x 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.x 2.x
# Navigate to the new working tree
cd .worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-618-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 6c4400d573d8711ab3f71f603b9c54c4a207fa3c
# Push it to GitHub
git push --set-upstream origin backport/backport-618-to-2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-618-to-2.x.

[opensearch-trigger-bot[bot]]

The backport to 2.12 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-2.12 2.12
# Navigate to the new working tree
cd .worktrees/backport-2.12
# Create a new branch
git switch --create backport/backport-618-to-2.12
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 6c4400d573d8711ab3f71f603b9c54c4a207fa3c
# Push it to GitHub
git push --set-upstream origin backport/backport-618-to-2.12
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.12

Then, create a pull request where the base branch is 2.12 and the compare/head branch is backport/backport-618-to-2.12.