HPCC-10570 Fix confusion over DeleteOwnedSubFiles/RemoveOwnedSubFiles

Function was added with a different name (and semantics) in 4.0.4 vs 4.2

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5234 from richardkchapman/deleteOwned

HPCC-10570 Fix confusion over DeleteOwnedSubFiles/RemoveOwnedSubFiles

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>