Bug 28376: (follow-up) Replace jQueryUI date/timepicker with Flatpickr

Remove uneeded include of flatpickr.min.js (we load it from
calendar.inc)

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

koha-tmpl/intranet-tmpl/prog/en/modules/admin/categories.tt

@@ -683,7 +683,6 @@
 [% MACRO jsinclude BLOCK %]
     [% Asset.js("js/admin-menu.js") | $raw %]
     [% Asset.js("js/messaging-preference-form.js") | $raw %]
-    [% Asset.js("lib/flatpickr/flatpickr.min.js") | $raw %]
     [% INCLUDE 'calendar.inc' %]
     [% INCLUDE 'datatables.inc' %]
     [% INCLUDE 'columns_settings.inc' %]