fix(aio): remove links from sub-menu toggles (#21695)

Navigating to a document while trying to expand or collapse a sub-menu
is undesirable and confusing. All sub-menu toggles should have no other
effect than expanding/collapsing the corresponding sub-menu.

PR Close #21695

aio/src/styles/1-layouts/_sidenav.scss

@@ -128,6 +128,12 @@ button.vertical-menu-item {
   transition-timing-function: ease-out;
 }
 
+.no-animations {
+  .heading-children.expanded, .heading-children.collapsed {
+    transition: none! important;
+  }
+}
+
 .level-1 {
   font-family: $main-font;
   font-size: 14px;