[SPARK-20119][TEST-MAVEN] Fix the test case fail in DataSourceScanExecRedactionSuite

### What changes were proposed in this pull request?
Changed the pattern to match the first n characters in the location field so that the string truncation does not affect it.

### How was this patch tested?
N/A

Author: Xiao Li <gatorsmile@gmail.com>

Closes #17448 from gatorsmile/fixTestCAse.