Fix Java SimpleApp spark application

## What changes were proposed in this pull request?

Add missing import and missing parentheses to invoke `SparkSession::text()`.

## How was this patch tested?

Built and the code for this application, ran jekyll locally per docs/README.md.

Author: Christiam Camacho <camacho@ncbi.nlm.nih.gov>

Closes #18795 from christiam/master.