chore(deps,flink): update confluent-kafka requirement

Updates the requirements on [confluent-kafka](https://github.com/confluentinc/confluent-kafka-python) to permit the latest version.
- [Release notes](https://github.com/confluentinc/confluent-kafka-python/releases)
- [Changelog](https://github.com/confluentinc/confluent-kafka-python/blob/master/CHANGELOG.md)
- [Commits](confluentinc/confluent-kafka-python@v2.15.0...v2.15.1)

---
updated-dependencies:
- dependency-name: confluent-kafka
  dependency-version: 2.15.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

src/agentflow_runtime/processing/flink_jobs/requirements.txt

@@ -14,6 +14,6 @@
 # libraries carry the same bounds as core pyproject.toml so both runtimes
 # accept the same model/config payloads.
 apache-flink==2.3.0
-confluent-kafka>=2.15.0,<3
+confluent-kafka>=2.15.1,<3
 pydantic>=2.13.5,<3
 structlog>=26.1.0,<27