[FIX] hr_holidays: handle all holiday types in onchange

The holiday_type can be 'employee', 'company', 'department' or 'category'.
However in the onchange of holiday_type, for some reason nothing was done
in the case of the 'company' value.

As a result, the default 'employee' would set the employee_id,
but then changing the type to company would not remove the employee_id.
It follows that the lucky employee would get two allocations instead of one.

opw 1938498

closes odoo/odoo#31656

Signed-off-by: Nans Lefebvre (len) <len@odoo.com>

addons/hr_holidays/models/hr_leave_allocation.py

@@ -251,7 +251,7 @@ class HolidaysAllocation(models.Model):
             if self.env.user.employee_ids:
                 self.department_id = self.department_id or self.env.user.employee_ids[0].department_id
             self.employee_id = None
-        elif self.holiday_type == 'category':
+        else:
             self.employee_id = None
             self.department_id = None