[FIX] hr_holidays: Wrong computation of leave duration
[FIX] hr_holidays: Wrong computation of leave duration

When all days in a calendar don't have the same schedule, it's wrong
to compute the leave duration with the average working time hour per day.

opw:1909145

closes odoo/odoo#29313
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo