[FIX] web: kanbancard reestablish 16.0 outline effect

Since milk redesign the kanbancard lost their outline bottom on focus
state.

Previous fixes where applied to solve this issue in commit[1]
and commit[2]. These fixes were a Catch-22:
fixing a behavior here, creating an issue there (double borders,
issue on drag..) which lead to more custom code.

In this commit, we remove the code added by the previous fixes and apply
a solution used in version 16.0 and prior. Relying on a negative margin
to hide the border of the following `kanban_record` and applying an
outline effect and a greater `z-index` on focus to make it appear on
top of the border. This z-index is set to 2 to compensate the
`z-index-1` on the kanban column when a card is focused and dragged.

[1]: odoo/odoo@d8fcc218bc
[2]: odoo/odoo@2495bfa725

task-3580229

closes odoo/odoo#148869

X-original-commit: ca388322327379e470e76f3a3c6ee2b2271e3895
Signed-off-by: Pierre Paridans (app) <app@odoo.com>

addons/web/static/src/views/kanban/kanban_controller.scss

@@ -77,6 +77,7 @@
     .o_kanban_record {
         position: relative;
         min-width: 150px;
+        margin: 0 0 (-$border-width);
 
         > div:not(.o_dropdown_kanban) {
             padding: var(--KanbanRecord-padding-v) var(--KanbanRecord-padding-h);
@@ -392,6 +393,8 @@
 
         &:focus-visible,
         &:focus-within {
+            z-index: 2;
+
             @include global-click-selector {
                 outline: thin solid mix($o-main-link-color, map-get($grays, "300"));
                 outline-offset: -1px;
@@ -489,10 +492,6 @@
 
         .o_kanban_record {
             width: 100%;
-
-            & + .o_kanban_record:not(.o_dragged) .oe_kanban_card {
-                border-top: none;
-            }
         }
 
         .o_kanban_group {