Bugfix: remove assert on non-empty translog reader list

[sachinpkale]

Description

• Currently, in RemoteFsTranslog, as part of trimUnreferencedReaders, we delete stale remote primary terms.
• The deleteStaleRemotePrimaryTerms function assumes existing list of translog readers to be non empty and have a corresponding assert.
• This assert results in flaky behavior of tests like: [BUG] org.opensearch.index.translog.RemoteFSTranslogTests.testConcurrentWriteViewsAndSnapshot is flaky #9455
• In this PR, we remove the assert and return from deleteStaleRemotePrimaryTerms if translog reader list is empty.
• It is safe to remove the assert as translog reader list can be empty due to super.trimUnreferencedReaders() that is executed prior.

Related Issues

Resolves #9455

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/23118/
• CommitID: 5bc6f99
  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?

[opensearch-trigger-bot]

Compatibility status:

Checks if related components are compatible with change 784a473

Incompatible components

Incompatible components: [https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/asynchronous-search.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/performance-analyzer-rca.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.cluster.allocation.AwarenessAllocationIT.testThreeZoneOneReplicaWithForceZoneValueAndLoadAwareness

• URL: https://build.ci.opensearch.org/job/gradle-check/23119/
• CommitID: 2ab0e62
  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

Merging #9458 (175ba4d) into main (784a473) will decrease coverage by 0.04%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##               main    #9458      +/-   ##
============================================
- Coverage     71.18%   71.14%   -0.04%     
+ Complexity    57453    57432      -21     
============================================
  Files          4776     4776              
  Lines        270813   270815       +2     
  Branches      39582    39582              
============================================
- Hits         192780   192680     -100     
- Misses        61871    61928      +57     
- Partials      16162    16207      +45     

Files Changed	Coverage Δ
...rg/opensearch/index/translog/RemoteFsTranslog.java	70.10% <0.00%> (-0.78%)	⬇️

... and 438 files with indirect coverage changes

[opensearch-trigger-bot]

Compatibility status:

Checks if related components are compatible with change 61c5f17

Incompatible components

Incompatible components: [https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/asynchronous-search.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/reporting.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/23131/
• CommitID: 175ba4d

[sachinpkale]

Byapssing codecov/patch as the changes fix a flaky test.