Bug 14949: Remove remaining C4::Dates and fix display in admin/categorie.pl

Bug 14949: Remove remaining C4::Dates and fix display in admin/categorie.pl

This patch removes a remaining C4::Dates from admin/categroie.pl and fixes
the display of "Enrollment period" on the confirmation screen for deleting.

To verify and test pls. refer to comments #5 and #6

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as advertised

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>