[FIX] l10n_be_hr_payroll: Fix 9c5f930

Purpose
=======

Since 9c5f930, the double holiday is computed from the wage with holidays.

When we compute the employer costs, we should take the original wage,
not the adapted one, to keep fix employer costs, whatever the amount
of days the employee takes.

closes odoo/odoo#30149

addons/l10n_be_hr_payroll/models/l10n_be_hr_payroll.py

@@ -153,13 +153,13 @@ class HrContract(models.Model):
             )
 
     @api.depends('yearly_cost_before_charges', 'social_security_contributions', 'wage',
-        'social_security_contributions', 'double_holidays', 'warrants_cost', 'meal_voucher_paid_by_employer')
+        'social_security_contributions', 'warrants_cost', 'meal_voucher_paid_by_employer')
     def _compute_final_yearly_costs(self):
         for contract in self:
             contract.final_yearly_costs = (
                 contract.yearly_cost_before_charges +
                 contract.social_security_contributions +
-                contract.double_holidays +
+                contract.wage * 0.92 +
                 contract.warrants_cost +
                 (220.0 * contract.meal_voucher_paid_by_employer)
             )