[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


The change done to support count update, we want to remove kaban subtitle but we want to keep counter updated, if I move record from one group to another group counter should be visible and old group should be deducted by 1 and new group should increased by 1(where record dragged), on_record_moved returns nothing, hence I changed on_record_moved and return deferred so that we can add callback when record moved is succeeded we can update the counter in both group