Bug 22009: Fix error messages for filing rules and splitting rules.

Bug 22009: Fix error messages for filing rules and splitting rules.

Some error messages were doubled up with different error codes.

To test:
I am not sure how to trigger those from the GUI, might
require a code review/code changes.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 558742577d3902cd5e2abf5c3f165c6425e163da)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>