[FLINK-35012][table] Fix flaky ChangelogNormalizeRestoreTest by adding padding records to prevent mini-batch merging

[Au-Miner]

What is the purpose of the change

Fix the flaky ChangelogNormalizeRestoreTest.testRestore failure for the changelog-normalize-source-mini-batch variant. The test intermittently fails because INSERT "six" and DELETE "six" can end up in the same mini-batch, causing addInput to overwrite the INSERT with the DELETE, resulting in both records being silently dropped.

Brief change log

• [ChangelogNormalizeTestPrograms.java] Added one no-op DELETE padding record ("seven") to AFTER_DATA to ensure INSERT "six" and DELETE "six" are always separated into different mini-batches by CountBundleTrigger(size=2), regardless of processing-time watermark timing.

Verifying this change

This change is a test-only fix. The existing ChangelogNormalizeRestoreTest.testRestore test validates correctness. The padding DELETE records target non-existent keys, so they produce no output and do not affect AFTER_OUTPUT expectations.

Does this pull request potentially affect one of the following parts

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Currentity, Coordination, Zookeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 1529c08 Azure: SUCCESS

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