[FIX] hr_holidays: approval link

The approval link received by a manager doesn't take into account the
double approval configuration of the holiday type.

opw-741558

addons/hr_holidays/controllers/main.py

@@ -12,7 +12,7 @@ class HrHolidaysController(http.Controller):
         comparison, record, redirect = MailController._check_token_and_record_or_redirect('hr.holidays', int(res_id), token)
         if comparison and record:
             try:
-                record.action_validate()
+                record.action_approve()
             except Exception:
                 return MailController._redirect_to_messaging()
         return redirect