arrow

ARROW-17858: [C++] Compilating warning in arrow/csv/parser.h (#14445)

This PR modifies the `DecorateWithRowNumber` method in the `DataBatch` class to return an unknown error to avoid getting a compilation warning.

Lead-authored-by: Sanjiban Sengupta <sanjiban.sg@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>