During 6.8.1 conversion, an error is reported when the version is running on JDK21. **Error: Unsupported class file major version 65**

[njxtest]

During 6.8.1 conversion, an error is reported when the version is running on JDK21. Error: Unsupported class file major version 65

[ERROR] Tests run: 3589, Failures: 35, Errors: 5, Skipped: 6

[njxtest]

I need check whether flowable-engine(6.8.1) can sucess run with JDK21. So, I need to compile flowable-engine and run it's test case to premiss it 100% passed.