[FIX] web, website: adapt accordion to bootstrap update

Some update to the accordion component made it incompatible with some of
our customization.

addons/web/static/src/scss/bootstrap_review.scss

@@ -31,6 +31,15 @@
         @include border-bottom-radius($card-inner-border-radius);
     }
 }
+.accordion {
+    .collapsing, .collapse.show {
+        > .card-body:first-child {
+            // Above background color would overflow on the card-header border
+            // without this
+            margin-top: $card-border-width;
+        }
+    }
+}
 
 // Modify modals so that their scrollable element is the modal-body (except in
 // mobile).

addons/website/static/src/scss/website.scss

@@ -392,8 +392,6 @@ table.table_desc tr td {
 // FAQ
 .s_faq_collapse {
     .accordion .card {
-        border-bottom: 1px solid rgba(0, 0, 0, 0.125);
-        margin: 5px 0;
         .card-header {
             cursor: pointer;
             display: inline-block;