Coming from opensearch-project/opensearch-plugins#132, remove support for JDK 14.

In OpenSearch 2.0 we are building the complete distribution and every component with JDK 11, and testing and bundling JDK 17. Support for JDK 14, 15 and other non-LTS versions can be dropped. Remove building and testing with these JDKs from CI.

See https://opensearch.org/blog/technical-post/2022/03/opensearch-java-runtime/ for more information.