[MINOR][SQL] Fixing the typo in unit test

## What changes were proposed in this pull request?

Fixing the typo in the unit test of CodeGenerationSuite.scala

## How was this patch tested?
Ran the unit test after fixing the typo and it passes

Author: Srinivasa Reddy Vundela <vsr@cloudera.com>

Closes #14989 from vundela/typo_fix.