Closing the directory reader to fix test

[expani]

./gradlew ':server:test' --tests "org.opensearch.search.aggregations.startree.RangeAggregatorTests.testRangeAggregation" -Dtests.seed=A5CF5DD34EE06092 -Dtests.security.manager=true -Dtests.jvm.argline="-XX:TieredStopAtLevel=1 -XX:ReservedCodeCacheSize=64m" -Dtests.locale=nl -Dtests.timezone=Asia/Ust-Nera -Druntime.java=21

Able to consistently reproduce failure locally and the test fixes after change.

Related Issues

#17928

[github-actions]

❌ Gradle check result for fe94dd6: 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 fe94dd6: 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 72.47%. Comparing base (5799fe7) to head (fe94dd6).
Report is 11 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #17968      +/-   ##
============================================
- Coverage     72.57%   72.47%   -0.11%     
+ Complexity    67066    67043      -23     
============================================
  Files          5470     5475       +5     
  Lines        309697   309921     +224     
  Branches      45045    45066      +21     
============================================
- Hits         224776   224615     -161     
- Misses        66602    66965     +363     
- Partials      18319    18341      +22     

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[harshavamsi]

Thanks!