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Description
This updates the CI system to use jdk-21, which is latest LTS supported version. Coming from https://github.com/opensearch-project/OpenSearch/issues/10334
Backport of https://github.com/opensearch-project/geospatial/pull/599
Check List
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.