Use apps/v1 API group whenever possible (#8055)

The use of extensions/v1beta1, apps/v1beta1 and apps/v1beta2 API
groups should be discouraged.

Closes: #8049

docs/concepts/workloads/controllers/garbage-collection.md

@@ -52,7 +52,7 @@ kind: Pod
 metadata:
   ...
   ownerReferences:
-  - apiVersion: extensions/v1beta1
+  - apiVersion: apps/v1
     controller: true
     blockOwnerDeletion: true
     kind: ReplicaSet

docs/concepts/workloads/controllers/my-repset.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: ReplicaSet
 metadata:
   name: my-repset