[Backport 2.x] Fix RemoteCloneIndex flaky test by using sync FS repo

[opensearch-trigger-bot]

Backport 47171f8 from #15037.

[github-actions]

❌ Gradle check result for 302ae83: 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 302ae83: 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 302ae83: 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 71.16%. Comparing base (e03e093) to head (302ae83).
Report is 1 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #15096      +/-   ##
============================================
- Coverage     71.71%   71.16%   -0.55%     
+ Complexity    62868    62331     -537     
============================================
  Files          5125     5125              
  Lines        294586   294588       +2     
  Branches      42934    42934              
============================================
- Hits         211260   209650    -1610     
- Misses        65600    67207    +1607     
- Partials      17726    17731       +5     

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