Mute flaky CompositeIndexWriterForAppendTests

[andrross]

Muting the entire class because some of the failures are file leaks detected during teardown, so I'm not sure which test method is causing the problem.

CompositeIndexWriterForAppendTests > classMethod FAILED
    java.lang.RuntimeException: file handle leaks:
[FileChannel(/var/jenkins/workspace/gradle-check/search/server/build/testrun/test/temp/org.opensearch.index.engine.CompositeIndexWriterForAppendTests_5D4C13243992BC3C-001/index-MMapDirectory-001/write.lock)]

Related to #20005

Check List

• Functionality includes testing.

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.

[andrross]

FYI @RS146BIJAY

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

❌ Gradle check result for 9522338: 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 9522338: 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 73.32%. Comparing base (28fa177) to head (9522338).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #20903      +/-   ##
============================================
- Coverage     73.32%   73.32%   -0.01%     
- Complexity    72272    72293      +21     
============================================
  Files          5797     5802       +5     
  Lines        330323   330405      +82     
  Branches      47676    47686      +10     
============================================
+ Hits         242215   242275      +60     
- Misses        68663    68672       +9     
- Partials      19445    19458      +13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[RS146BIJAY]

Sorry I missed this test case fixes. I will fix this issue in another day or tow and raise the PR. Thanks @andrross for muting the test cases in the mean time.