HPCC-11721 Remove maxlength dependency in the field mapping code

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-11721 Remove unnecessary code

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6093 from ghalliday/issue11721

HPCC-11721 Remove maxlength dependency in the field mapping code

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>