[5.1] collapsed sidebar menu [a11y] (#43137)

Author: brianteeman

build/media_source/templates/administrator/atum/scss/_variables.scss

@@ -215,6 +215,7 @@ $atum-colors: (
   main-nav-ul-bg:                  var(--template-bg-dark-75),
   main-nav-divider-bg:             var(--template-bg-dark-60),
   main-nav-item-title:             var(--template-bg-dark-30),
+  main-nav-item-title-hvr-bg:      var(--template-bg-dark-60),
   main-nav-mm-active-bg:           var(--template-bg-dark-70),
   main-nav-mm-active-quicktask-bg: var(--template-bg-dark-60),
   main-nav-badge:                  var(--template-bg-dark-60),

build/media_source/templates/administrator/atum/scss/blocks/_sidebar.scss

@@ -291,7 +291,6 @@
 @if $enable-dark-mode {
   @include color-mode(dark) {
     .sidebar-wrapper {
-      overflow: hidden;
       border: 1px solid rgba(255, 255, 255, .05);
       box-shadow: none;
       .main-nav {