Bug 15361: Translatability: Fix issue on Administration Columns settings

 Bug 15361: Translatability: Fix issue on Administration Columns settings

This patch rewords the following sentence that is not correctly translatable due to
splitting b tags:
Changes made below will only apply to item subfields that are mapped to the items table.

To test:
- Apply patch
- Verify that the rewording makes sese and that no sentences are split by tags.

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Rewording message displayed Ok for translation purpose

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit 4983d5c4b9786479f849494efd3048f65ba26008)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>