[IMP] web: remove legacy dropdown css

Adapt SearchBar accordingly to properly keep the highlight effect during
keyboard navigation (cf. removed comments in dropdown.scss).

task-3439226

Part-of: odoo/odoo#133289

addons/web/static/src/legacy/scss/dropdown.scss

@@ -57,38 +57,3 @@
         }
     }
 }
-
-// = Legacy submenus
-
-// TODO probably remove those next rules that target dropdown main classes once
-// the backend searchbar has been refactored to use OWL dropdown components and
-// to stop using the BS4 "focus" class which is not part of BS5 anymore.
-// See the commit that introduced this comment for more details.
-
-.dropdown-menu {
-    .dropdown-toggle:focus, .dropdown-item:focus {
-        background-color: transparent;
-        outline: none;
-    }
-    .dropdown-toggle.focus, .dropdown-item.focus {
-        background-color: $dropdown-link-hover-bg;
-    }
-}
-
-.dropdown-item:not(.disabled):not(:disabled) {
-    cursor: pointer;
-}
-
-button.dropdown-toggle {
-    &.active, &:hover, &:focus, &:active {
-        outline: none;
-        box-shadow: none !important;
-    }
-    &.dropdown-item {
-        &::after, &::before {
-            // Changes the placement of bootstrap dropdown carets for subdropdowns
-            @include o-position-absolute($right: 0, $top: 0);
-            transform: translate(-.6em, .6em) #{"/*rtl:translate(.6em, .6em) scaleX(-1)*/"};
-        }
-    }
-}

addons/web/static/src/search/search_bar/search_bar.xml

@@ -64,7 +64,7 @@
     </t>
 
     <t t-name="web.SearchBar.Items">
-        <ul class="dropdown-menu o_searchview_autocomplete dropdown-menu show" role="menu">
+        <ul class="o-dropdown--menu dropdown-menu o_searchview_autocomplete show" role="menu">
             <t t-foreach="items" t-as="item" t-key="item.id">
                 <li class="o_menu_item dropdown-item"
                     t-att-class="{ o_indent: item.isChild, focus: item_index === state.focusedIndex}"