Merge pull request #14408 from vsn4ik/dropdown_menu_disabled_style

Refactor dropdown.less. Optimize ".dropdown-menu > .disabled" selector.

less/dropdowns.less

@@ -103,9 +103,8 @@
   &:focus {
     color: @dropdown-link-disabled-color;
   }
-}
-// Nuke hover/focus effects
-.dropdown-menu > .disabled > a {
+
+  // Nuke hover/focus effects
   &:hover,
   &:focus {
     text-decoration: none;