[FIX] web: kanban containment

Set up the following kanban columns:

| Col 1 | Col 2 | Col 3 | Col 4 | Col 5 | Col 6 | F |
|       |       |       |       |       |  Card |   |

<------- Screen width ---------->

Col x are unfolded columns.
F is a folded colum.

Moving the Card from Col 6 to F is impossible: the card won't go 'out of
the screen' on the right, which prevents its center to reach F.

Commit 5ba6d93810 deactivates the drag & drop on read-only fields.
In order to restrict the kanban cards displacements, the `containment`
attribute is used to either restrict the displacement:
- in `o_kanban_view` if draggable
- in the parent if not (to allow the resequence)

The class `o_kanban_view` is too restrictive: when movind the card to
the folded column F, the card must go out of `o_kanban_view`.

opw-803929

addons/web/static/src/js/views/kanban/kanban_column.js

@@ -93,7 +93,7 @@ var KanbanColumn = Widget.extend({
             // should find a way to use the touch events to make sortable work.
             this.$el.sortable({
                 connectWith: '.o_kanban_group',
-                containment: this.draggable ? '.o_kanban_view' : 'parent',
+                containment: this.draggable ? false : 'parent',
                 revert: 0,
                 delay: 0,
                 items: '> .o_kanban_record:not(.o_updating)',