Bump checkstyle from 6.17 to 8.29 in /java-server

Bumps [checkstyle](https://github.com/checkstyle/checkstyle) from 6.17 to 8.29.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](https://github.com/checkstyle/checkstyle/compare/checkstyle-6.17...checkstyle-8.29

)

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