[FLINK-26531][kafka] KafkaWriterITCase.testMetadataPublisher failed on azure

[JingsongLi]

What is the purpose of the change

Fix unstable case: KafkaWriterITCase.testMetadataPublisher

Brief change log

After the sink v2 refactoring, precommit is divided into two separate methods: flush and precommit.
In this test, we should call flush instead of precommit.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)

[flinkbot]

CI report:

• a259c21 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[gaoyunhaii]

Thanks @JingsongLi for the fix, LGTM