## What changes were proposed in this pull request?
500L << 20 is actually pretty close to 32-bit int limit. I was trying to increase this to 500L << 23 and got negative numbers instead.

## How was this patch tested?
I'm only modifying test code.

Author: Reynold Xin <rxin@databricks.com>

Closes #11839 from rxin/SPARK-14018.