HPCC-11867 Clean up calls to CStringArray::sort

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6196 from ghalliday/issue11867

HPCC-11867 Clean up calls to CStringArray::sort

Reviewed-By: Kevin Wang <kevin.wang@lexisnexis.com>
Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>