Fix a bunch of UI nits in sheriff-o-matic.

Tools/GardeningServer/ui/ct-builder-grid.html

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <link rel="import" href="ct-builder.html">
 
 <!-- Table of failure types, listing the failing builders for each type. -->
 <polymer-element name="ct-builder-grid" attributes="failures">
   <template>
     <style>
       table {
         border-collapse: collapse;
         font-size: 11px;
         table-layout: fixed;
         width: 350px;
       }
 
-      tbody tr {
-        border-top: 1px solid #eee;
-      }
-
       tbody td:first-child {
         width: 20%;
       }
 
       tbody td {
         padding: 2px;
         vertical-align: top;
         width: 40%;
       }
 
@@ skipping 121 matching lines @@
           if (!config.builders[builderName])
             return;
           building[builderName] =
               {'debug': config.builders[builderName].debug};
         });
         return building;
       },
     });
   </script>
 </polymer-element>