[FLINK-34124] Disable Kyro by default

[X-czh]

What is the purpose of the change

Disable Kyro by default as per FLIP-398.

Brief change log

Disable Kyro by default.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

Updated serialization document accordingly.

[flinkbot]

CI report:

• 3fa70c2 Azure: FAILURE

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