Bug 29695: Remove C4::Reports::Guided::_get_column_defs

Bug 29695: Remove C4::Reports::Guided::_get_column_defs

This subroutine was mostly the same as GetColumnDefs, we replace it
identically as in the previous patch.

Test plan:
Translate some strings in another language
 % gulp po:update --lang es-ES
 % cd misc/translate
 # Translate the relevant strings in po/es-ES-messages.po
 # For instance "Alternate contact: Surname"
 % perl translate install es-ES

Select the language for the interface (enable it in the 'language' syspref
first)

Create a new guided report and confirm that the columns for the borrowers
table are translated

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>