[FLINK-29705][k8s] Document the least access with RBAC setting for na…

[Mrart]

What is the purpose of the change

Document the least access with RBAC setting for native K8s integration

Brief change log

Document the least access with RBAC setting for native K8s integration

Verifying this change

Please make sure both new and modified tests in this PR follows the conventions defined in our code quality guide: https://flink.apache.org/contributing/code-style-and-quality-common.html#testing

(Please pick either of the following options)
no

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

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no )
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: ( no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (docs)

[flinkbot]

CI report:

• 4e1b22e Azure: SUCCESS

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