[MINOR][DOCS][STREAMING] Minor docfix schema of csv rather than parquet in comments

## What changes were proposed in this pull request?

Fix parquet to csv in a comment to match the input format being read.

## How was this patch tested?
N/A (doc change only)

Author: Holden Karau <holden@us.ibm.com>

Closes #14274 from holdenk/minor-docfix-schema-of-csv-rather-than-parquet.