Update Apache Flink resources after update to version 1.20.1

[amotl]

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Apply maintenance to the Apache Flink resources.

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@matriv updated to latest Flink stable yesterday. Thank you very much.

• Upgrade to latest flink (1.20.1) cratedb-flink-jobs#60

He also suggested:

After this update on Flink jobs, I think we should release it and then update the rig in framework/flink here to use the new release.

[amotl]

The update to version 0.6 fails. I did not investigate yet, why. The error output is a bit sparse.

• Kafka/Flink: Update to cratedb-flink-jobs-0.6 #859