pagure/templates/_render_repo.html: Ensure "No activity" rows get removed on subsequent updates

Fixes #4429
Merges #4439

pagure/templates/_render_repo.html

@@ -378,7 +378,7 @@
               }
                else {
                   $('#user-activity-body').append(
-                  '<div class="list-group-item">No activity recorded on that day</div>'
+                  '<div class="list-group-item activity-item">No activity recorded on that day</div>'
                 );
               }
             }