[cleanup][admin]cleanup unused sync method in NamespacesBase

[AnonHxy]

Motivation

Cleanup unused sync method in NamespacesBase

Modifications

Removing validatePolicies and internalSetTopicDispatchRate

Verifying this change

• [ ] Make sure that the change passes the CI checks.

Documentation

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Matching PR in forked repository

PR in forked repository: https://github.com/AnonHxy/pulsar/pull/2