[FLINK-37314][Documentation] Fix the definition of lateness to t_w - t instead of t - t_w

[Myracle]

Fix the definition of lateness to t_w - t instead of t - t_w

• • The position t and t_w should change.So, if t_w - t{{ > 0}} then the element is considered late. An event which timestamp is smaller than watermark should be a latecomer.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

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)

[flinkbot]

CI report:

• 451c18e Azure: FAILURE

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[Myracle]

@flinkbot run azure

[1996fanrui]

Thanks for the fix!

It seems CI is failed by some python tests, it is not related to current change, merging