[FIX] board: dashboard darkmode

Steps to reproduce:
- add elements to dashboard
- enter dashboard and enable darkmode

Bug:
titles are unreadable because background is white

Fix:
remove CSS property

closes odoo/odoo#110201

X-original-commit: 5b56f1891d618008678d70ad125ad1393abe352b
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>

addons/board/static/src/board_controller.scss

@@ -27,10 +27,7 @@
 }
 
 .o-dashboard-action {
-    background-color: white;
     align-self: start;
-    border: 1px solid;
-    border-color: #e5e5e5 #dbdbdb #d2d2d2;
 
     > .o_view_controller {
         padding: 0 12px 12px 12px;

addons/board/static/src/board_controller.xml

@@ -32,7 +32,7 @@
             <t t-foreach="board.columns" t-as="column" t-key="column_index">
                 <div t-if="column_index lt board.colNumber" class="o-dashboard-column h-100" t-att-data-idx="column_index">
                     <t t-foreach="column.actions" t-as="action" t-key="action.id">
-                        <div class="o-dashboard-action mx-3 my-1" t-att-data-idx="action_index">
+                        <div class="o-dashboard-action mx-3 my-1 bg-view border" t-att-data-idx="action_index">
                             <h3 t-attf-class="o-dashboard-action-header {{action.title ? '' : 'oe_header_empty'}} p-2 m-2">
                                 <span> <t t-esc="action.title"/> </span>
                                 <span class="btn float-end p-1 text-muted" t-on-click="() => this.closeAction(column, action)"><i class="fa fa-close"/></span>