Update sidekiq.md

doc/administration/sidekiq.md

@@ -25,8 +25,9 @@ you want using steps 1 and 2 from the GitLab downloads page.
 
    ## Optional: Enable extra Sidekiq processes
    sidekiq_cluster['enable'] = true
-   sidekiq_cluster['enable'] = true
-     "elastic_indexer"
+   sidekiq['queue_groups'] = [
+     "elastic_indexer",
+     "*"
    ]
    ```