It's confusing to see the timestamp of started_at if the status says "completed" (#19551)

fixes https://github.com/elastic/kibana/issues/17912

x-pack/plugins/reporting/public/views/management/jobs.html

@@ -30,10 +30,16 @@
             </div>
             <div
               class="metadata"
-              ng-if="job.status !== 'pending'"
+              ng-if="job.status === 'processing'"
               >
               {{ job.started_at | date : 'yyyy-MM-dd @ h:mm a' }}
             </div>
+            <div
+              class="metadata"
+              ng-if="job.status === 'completed' || job.status === 'failed'"
+            >
+              {{ job.completed_at | date : 'yyyy-MM-dd @ h:mm a' }}
+            </div>
           </td>
           <td class="actions">
             <button