[DOC]: Pipeline help strings need to be updated

[dagardner-nv]

How would you describe the priority of this documentation request

High

Please provide a link or source to the relevant docs

n/a

Describe the problems in the documentation

Currently the help string for pipeline-nlp provides some misleading/out of date output.

Specifically it implies that from-file and from-kafka are the only two source stages, that the deserialize stage is required.

(Optional) Propose a correction

Update each of the three pipeline help strings.

Code of Conduct

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