Iceberg BOM references unpublished Kafka Connect runtime artifact

[manuzhang]

Apache Iceberg version

1.11.0 (latest release) and main

Query engine

Kafka Connect

Please describe the bug 🐞

The Iceberg BOM includes org.apache.iceberg:iceberg-kafka-connect-runtime, but
that Maven artifact is not published; its 1.11.0 POM
returns 404.

The runtime project disables Maven publishing
because it produces ZIP distributions. The published iceberg-kafka-connect,
iceberg-kafka-connect-events, and iceberg-kafka-connect-transforms artifacts
should remain in the BOM.

The BOM should exclude iceberg-kafka-connect-runtime until that artifact is
published. Related: #14986.