[FIX] hr_holidays: create activity if leave has to be validated

Issue:
------
When a leave is created, a notification is only sent
if a "Time Off Officer" is defined (`responsible_ids`).

However, if we choose the approval option with
the value: "By Employee's Approver",
the leave manager must be notified even if
there is no "Time Off Officer".

Solution:
---------
Give the option of creating notifications in all cases where validation
is required for the leave type.

opw-3412841

closes odoo/odoo#135310

X-original-commit: 1428505b0aaf6a1d3cf778bdb6137bea9ec6283e
Signed-off-by: Sofie Gvaladze (sgv) <sgv@odoo.com>
Signed-off-by: Thomas Lefebvre (thle) <thle@odoo.com>

addons/hr_holidays/models/hr_leave.py

@@ -1555,7 +1555,7 @@ class HolidaysRequest(models.Model):
             if holiday.state == 'draft':
                 to_clean |= holiday
             elif holiday.state == 'confirm':
-                if holiday.holiday_status_id.responsible_ids:
+                if holiday.holiday_status_id.leave_validation_type != 'no_validation':
                     user_ids = holiday.sudo()._get_responsible_for_approval().ids or self.env.user.ids
                     for user_id in user_ids:
                         activity_vals.append({