[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


oe_kanban_aggregates class not yet removed from css/sass file.