[Backport 2.19] Fix broken Gradle Spock's integration (skips Groovy tests)

[opensearch-trigger-bot]

Backport 753c135 from #19742.

[github-actions]

❌ Gradle check result for c8eac83: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for a68466b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❕ Gradle check result for 7fe37e0: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.04%. Comparing base (29450f0) to head (7fe37e0).
⚠️ Report is 1 commits behind head on 2.19.

Additional details and impacted files

@@             Coverage Diff              @@
##               2.19   #19771      +/-   ##
============================================
+ Coverage     72.03%   72.04%   +0.01%     
- Complexity    66024    66054      +30     
============================================
  Files          5342     5342              
  Lines        307283   307283              
  Branches      44845    44845              
============================================
+ Hits         221346   221389      +43     
+ Misses        67462    67409      -53     
- Partials      18475    18485      +10     

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