Fix issue 22209: [JAVA-gen] Standard Java inheritance, not an abstrac…

[Chhida]

*[BUG] [JAVA-gen] Standard Java inheritance, not an abstract schema wrapper !! #22209

This PR fixes this issue #22209

PR checklist

• [ x] Read the contribution guidelines.
• [ x] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• [x ] Run the following to build the project and update samples:

  ./mvnw clean package || exit
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  ./bin/utils/export_docs_generators.sh || exit
  

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[Chhida]

Hi @macjohnny,
I added a fix to avoid generating an abstract schema wrapper when using java langage (related to #22209). Tests and compilation pass locally. Could you please review and let me know if any further changes are needed before merging? Thanks!

[macjohnny]

cc java technical committee: @bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @martin-mfg (2023/08)