Revert change to spacing class names.

layouts/shortcodes/search.html

@@ -13,7 +13,7 @@
 <template>
   <article class="search-result list-view">
     <header>
-      <h2 class="title mt-s mb-xxs"><a href="#">Title here</a></h2>
+      <h2 class="title mt--s mb--xxs"><a href="#">Title here</a></h2>
       <div class="submitted"><time class="created-date">Date here</time></div>
     </header>
     <p class="content">Summary here</p>