[FIX] base_import : Add new date formats in import file

When you import a csv file with date format as DD.MM.YY you don't have
the option to select that specific date format , it's not in the list.

Steps to reproduce the error :
1-install accounting
2-go to accounting and select import on the Bank card
3-choose the file attached in the ticket
4-select Date in the field Buchungstag
5-you can see that it's date format is DD.MM.YY which doesn't exist in
the list of ´Date Format´ on the left.

Solution :
Added the required date format to the list.

opw-3425402

closes odoo/odoo#129101

Signed-off-by: Julien Castiaux (juc) <juc@odoo.com>