Make template statistics on the dashboard a table

It was a `<dl>` before which is kinda weird. Especially when the jobs
table was a real `<table>`.

It also means we can give it column headings so that new and invited
users have a better idea of what it is.

app/assets/stylesheets/views/dashboard.scss

@@ -49,7 +49,6 @@
     color: $govuk-blue;
     max-width: 100%;
     background: $white;
-    margin-bottom: $gutter-two-thirds;
   }
 
 }