[hotfix][datastream] Fix typos in DataStream

[libenchao]

What is the purpose of the change

Fix typos and outdated javadocs in DataStream

Brief change log

• Fix a few typos
• Fix outdated javadoc for windowAll

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, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

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

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[zentol]

please merge all of your PRs into a single one. #7867, #7868, #7869, #7870, #7871

[libenchao]

Thanks for the review @zentol , will do the merge.