The commit 79132f6 allowed multiple level for the subtasks, but a remnant from the ancient time was left. closes odoo/odoo#56104 Taskid: 2317929 X-original-commit: ace68ceceb92f8d7c16155fd72acd469424accd0 Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>