Bug 14954: (followup) Remove C4::Dates from holiday related files

Bug 14954: (followup) Remove C4::Dates from holiday related files

Followup for comment #10

To test:
- Go to Home > Tools > Calendar
- Add, edit, delete the different types of holidays and exceptions
- git grep 'C4::Calendar' and test such files
- git grep daysBetween to make sure that this sub is not used
- prove t/Calendar.t

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>