Pubsub Kafka: Docs for new certificate-based authentication in OIDC flow

[alicejgibbons]

What content needs to be created or modified?
https://docs.dapr.io/reference/components-reference/supported-pubsub/setup-apache-kafka/

Describe the solution you'd like
Updates from PR: https://github.com/dapr/components-contrib/pull/4057/files

Where should the new material be placed?
https://docs.dapr.io/reference/components-reference/supported-pubsub/setup-apache-kafka/

The associated pull request from dapr/dapr, dapr/components-contrib, or other Dapr code repos

Additional context

[alicejgibbons]

completed in #4922