docs: document replication factor and persistence size for future enhancements

[patsevanton]

This pull request adds comments to the values.yaml file for the Kafka configuration, specifically focusing on the replicationFactor and persistence.size settings. These comments are intended to guide future enhancements and provide context for potential adjustments to improve data reliability and fault tolerance in Kafka deployments.

Changes:

• Added a comment explaining the purpose of increasing the replicationFactor to enhance data reliability during Kafka pod failures.
• Added a comment suggesting an increase in persistence.size if the load on the Kafka controller increases.

Comments:

• replicationFactor: "Increasing the replicationFactor enhances data reliability during Kafka pod failures by replicating data across multiple brokers."
• persistence.size: "If the load on the Kafka controller increases, persistence.size must be increased."

Related Issues:

• kafka unstable #1458
• Kafka transactions log constantly growing up #1473

These comments will help maintainers and developers understand the rationale behind future changes and ensure that Kafka configurations remain robust and reliable.