In order to build and flink jobs compatible with flink 1.20 we need a new base image with flink 1.20.0
AC:
- Update https://gerrit.wikimedia.org/r/plugins/gitiles/operations/docker-images/production-images/+/refs/heads/master/images/flink/flink/ to pull flink 1.20.0
- Publish the corresponding image to docker-registry.wikimedia.org/flink:1.20.0-wmf0