Revert "Bump com.diffplug.spotless from 6.25.0 to 7.0.2"

[reta]

Reverts #17058, the plugin is unstable:

* What went wrong:
Execution failed for task ':distribution:tools:java-version-checker:spotlessJava'.
> Cannot fingerprint input property 'stepsInternalEquality': value 'com.diffplug.spotless.ConfigurationCacheHackList@d5fd99d3' cannot be serialized.

[1] https://build.ci.opensearch.org/job/gradle-check/52379/console
[2] equodev/equo-ide#188
[3] diffplug/spotless#2331

[github-actions]

✅ Gradle check result for a374ad2: SUCCESS

[opensearch-trigger-bot]

The backport to 2.x failed:

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

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-17074-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 f5c89c16c79871007be2c13f604314bd362a2bf4
# Push it to GitHub
git push --set-upstream origin backport/backport-17074-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-17074-to-2.x.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.61%. Comparing base (827aa63) to head (a374ad2).
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #17074      +/-   ##
============================================
+ Coverage     72.27%   72.61%   +0.34%     
- Complexity    65336    65663     +327     
============================================
  Files          5301     5301              
  Lines        303824   303824              
  Branches      44033    44033              
============================================
+ Hits         219587   220631    +1044     
+ Misses        66249    65435     -814     
+ Partials      17988    17758     -230     

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