[FIX] hr_holidays: date and datetime comparison
[FIX] hr_holidays: date and datetime comparison

The fields `validity_start` and `validity_stop` are `Date` fields, they
should therefore be compared to `datetime.date`.

opw-1918843

closes odoo/odoo#29834
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo