fix the 'to top' link; it wasn't appearing due to a previous CSS change

/* nav tree */

#side-nav, #devdoc-nav, #swapper,

#side-nav, #swapper,

#nav-tree, #tree-list {

  overflow:hidden;

  margin-left:0;

}

#devdoc-nav {

  overflow:visible !important; /* To keep the "to top" button visible */

}

#nav-tree ul {

  list-style:none;

  padding:0;