Bug 14931: Remove C4::Dates from files admin/aq*.pl

Bug 14931: Remove C4::Dates from files admin/aq*.pl

This patch removes C4::Dates from:

- admin/aqbudgets.pl
- admin/aqplan.pl
- admin/aqcontract.pl

To test:

- Apply patch

- Go to Home > Adminstration > Budgets > All funds
  (admin/aqbudgets.pl)
- Verify that everything displays as before

- Edit one of the funds and click on 'Planning - Plan by months'
  (admin/aqplan.pl)
- Verify that planning works as before

- Go to Home > Acquisitions, search for an active vendor and view the vendor
- Click on 'Contracts' at the left
  (admin/aqcontract.pl)
- Create and edit contracts and verify that it works OK.
  (Note: there is no help for this page, see Bug 14929)

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as advertised. Tested with dateformat syspref
Dates in planning by months not needed to be on iso format, aqplan.pl
uses instead Date::Calc

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>