[hotfix] Use simplifiedCondition to check for isAlwaysTrue in PushCalcPastChangelogNormalizeRule

[snuyanzin]

What is the purpose of the change

This is a small follow up for the commit aa97d86

Verifying this change

covered by existing tests in PushCalcPastChangelogNormalizeRuleTest

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)
• If yes, how is the feature documented? (not applicable)

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CI report:

• ed27235 Azure: SUCCESS

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