[FLINK-35382][test] Disable snapshot-file-merging in ChangelogCompabilityITCase

[ljz2051]

What is the purpose of the change

This pull request disable snapshot-file-merging config in ChangelogCompabilityITCase.

Brief change log

• Disable the FILE_MERGING_ENABLED config in ChangelogCompabilityITCase

Verifying this change

This change is already covered by existing tests (ChangelogCompabilityITCase).

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), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[ljz2051]

This pr is to resolve the unstable case (ChangelogCompatibilityITCase#testRestore).
@fredia Could you please help to review this fix?

[flinkbot]

CI report:

• dd21000 Azure: SUCCESS

Bot commands

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

[fredia]

@ljz2051 Thanks for the fix, LGTM