Fix pages that reference removed API groups

Quite some resources have been moved out of the `extensions` API group
since 1.18; the `apps/v1beta1` and `apps/v1beta2` group versions are
also dropped. This PR updates the pages which still reference such API
groups or group versions.

content/en/docs/concepts/cluster-administration/manage-deployment.md

@@ -323,7 +323,7 @@ When load on your application grows or shrinks, it's easy to scale with `kubectl
 kubectl scale deployment/my-nginx --replicas=1
 ```
 ```shell
-deployment.extensions/my-nginx scaled
+deployment.apps/my-nginx scaled
 ```
 
 Now you only have one pod managed by the deployment.