HPCC-11994 Improve no-files description in CT docs

Signed-off-by: Jim DeFabia <jamesdefabia@lexisnexis.com>
Merge pull request #6287 from JamesDeFabia/11994ImproveNoFilesDescriptionCTDocs

HPCC-11994 Improve no-files description in CT docs

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>