Fix flakiness in testDontAllowSwitchingCompatibilityModeForClusterWit…

[ltaragi]

…hMultipleVersions

Description

• Fixes the flakiness in org.opensearch.action.support.clustermanager.TransportClusterManagerNodeActionTests.testDontAllowSwitchingCompatibilityModeForClusterWithMultipleVersions.
• Was using randomCompatibleVersion(random(), version1) to pick version2 which does not guarantee version2 being different from version1 leading to an assertion failure at assert version1.equals(version2) == false
• Now specifically using two compatible and different OpenSearch versions for the purpose of the test

Related Issues

Resolves #13240

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• Public documentation issue/PR created

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[github-actions]

❌ Gradle check result for 8701a41: 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?

[ltaragi]

❌ Gradle check result for 8701a41: 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?

Flaky Tests: #11979, #12197

[github-actions]

✅ Gradle check result for 8701a41: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.43%. Comparing base (84679de) to head (8701a41).

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13281      +/-   ##
============================================
- Coverage     71.48%   71.43%   -0.05%     
+ Complexity    60670    60655      -15     
============================================
  Files          5040     5040              
  Lines        285456   285456              
  Branches      41338    41338              
============================================
- Hits         204044   203905     -139     
- Misses        64589    64705     +116     
- Partials      16823    16846      +23     

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