Few changes to column headings for clarity

- Removed "Failed" and "Total costs" on jobs page
- Changed "Sent" to "Processed" on jobs page.
- Removed "sent" from dashboard page on jobs table.

app/templates/partials/jobs/count.html

@@ -7,18 +7,7 @@
   </li>
   <li class="column-one-quarter">
     {{ big_number(
-      counts.sent, 'sent'
-    )}}
-  </li>
-  <li class="column-one-quarter">
-    {{ big_number(
-      counts.failed,
-      'failed'
-    )}}
-  </li>
-  <li class="column-one-quarter">
-    {{ big_number(
-      counts.cost, 'total cost'
+      counts.sent, 'processed'
     )}}
   </li>
 </ul>