[REM]web_kanban : Remove the subtitle from kanban view

Task: https://www.odoo.com/web#id=10048&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.iKws0chd8JBBQY5U


Instead of hiding element which shows length of kanban group we can update that kanban group column, if kanban record is moved from one group to another then group from which record is moved will be deducted and group to which record is moved will be increased by 1