Message consumption error: UnknownGroup (Local: Unknown group)

### Describe the bug When bumping from 2.8.2 to 2.8.3 I am periodically seeing this message for all the kafka sources. They seem to work, but the log seem suspicious. Is everything fine ? ### Error message/log ```text risingwave-meta-0 meta 2026-05-14T22:57:03.149096327Z WARN risingwave_connector::source::kafka::enumerator: failed to poll kafka client error=Message consumption error: UnknownGroup (Local: Unknown group) topic="foo" broker_address="redpanda.com:9092" ``` ### To Reproduce _No response_ ### Expected behavior _No response_ ### How did you deploy RisingWave? Kubernetes operator ### The version of RisingWave 2.8.3 ### Additional context _No response_