Remove unused java11 gradle configuration

[andrross]

The java11-specific sources were removed back in #2898 and as far as I can tell this configuration has been unneeded since that point.

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]

Compatibility status:

Checks if related components are compatible with change bbc7258

Incompatible components

Incompatible components: [https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/performance-analyzer-rca.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/k-nn.git]

[github-actions]

❕ Gradle check result for bbc7258: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.action.admin.cluster.node.tasks.ResourceAwareTasksTests.testTaskResourceTrackingDuringTaskCancellation

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 ✅

Comparison is base (2c8ee19) 71.46% compared to head (bbc7258) 71.27%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #11661      +/-   ##
============================================
- Coverage     71.46%   71.27%   -0.19%     
+ Complexity    59257    59132     -125     
============================================
  Files          4906     4906              
  Lines        278184   278184              
  Branches      40421    40421              
============================================
- Hits         198791   198272     -519     
- Misses        62959    63423     +464     
- Partials      16434    16489      +55     

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[reta]

Thanks @andrross !