[FIX] website_slides: Fix kanban view with group by

id=2069603

closes odoo/odoo#36603

Signed-off-by: Romain Libert (rli) <rli@odoo.com>

addons/website_slides/static/src/scss/slide_views.scss

 $o-kanban-large-record-width: 400px;
 
 .o_kanban_view.o_slide_kanban {
+    .o_kanban_group:not(.o_column_folded) {
+        width: $o-kanban-large-record-width + 2*$o-kanban-group-padding;
+    }
     .o_kanban_record {
-    	width: $o-kanban-large-record-width
+    	width: $o-kanban-large-record-width;
     }
 }