[FIX] hr_holidays_attendance: not blocking the refusal of leave

Steps to reproduce:
-------------------
- activate "Count Extra Hours" in Attendances settings;
- create attendances for an employee to create an overtime
(select one day of the weekend for example);
- create an Extra Hours type leave for this employee;
- remove the attendance that creates extra hours;

The extra hours of the employee is negative

- refuse the leave created before;

Issue:
------
A Validation Error occurs with the message:
"The employee does not have enough extra hours to extend this leave.".

Solution:
---------
Refuse leave based on extra hours
should not require any control
because we are not trying to extend leave.

opw-3342778

closes odoo/odoo#124959

X-original-commit: b86afb9f
Signed-off-by: Kevin Baptiste <kba@odoo.com>