message: Improve the navbar resize when not on a crate documentation
diff: <div class="container">
  <div class="pure-menu pure-menu-horizontal" role="navigation" aria-label="Main navigation">
  <form action="/releases/search" method="GET"
  - class="landing-search-form-nav {% if not is_latest_version %}not-latest{% endif %}">
  + class="landing-search-form-nav {% if is_latest_version is defined and not is_latest_version %}not-latest{% endif %}">
  {# The search bar #}
  <div id="search-input-nav" class="pure-menu-right">
  <label for="nav-search">
  