[DOC] Add delete_source option to Data Prepper's csv processor

[graytaylor0]

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A new parameter in the csv processor. (opensearch-project/data-prepper#4828).

Parameter description: If true, the configured source field will be deleted after the CSV data is parsed into separate fields.

*Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.

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