Remove option outformat="csv" in the next version

[HaleySchuhl]

Is your feature request related to a problem? Please describe.
Supporting JSON and CSV output is redundant ever since adding metadata to Outputs (like timestamp which should always be unique), so in version 5.0 of PlantCV we'd like to remove the CSV option and improve the usability of json2cvs to work regardless of parallel or "human-in-the-loop" jupyter notebook analyses.

Additional context
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