Update docs to use batch/v1beta1 cronjobs (#5475)

docs/user-guide/cronjob.yaml

@@ -1,18 +0,0 @@
-apiVersion: batch/v2alpha1
-kind: CronJob
-metadata:
-  name: hello
-spec:
-  schedule: "*/1 * * * *"
-  jobTemplate:
-    spec:
-      template:
-        spec:
-          containers:
-          - name: hello
-            image: busybox
-            args:
-            - /bin/sh
-            - -c
-            - date; echo Hello from the Kubernetes cluster
-          restartPolicy: OnFailure

docs/user-guide/kubectl-conventions.md

@@ -38,7 +38,8 @@ In order for `kubectl run` to satisfy infrastructure as code:
 * Deployment, using `extensions/v1beta1` endpoint - use `deployment/v1beta1` (default).
 * Deployment, using `apps/v1beta1` endpoint - use `deployment/apps.v1beta1` (recommended).
 * Job - use `job/v1`.
-* CronJob - use `cronjob/v2alpha1`.
+* CronJob - using `batch/v1beta1` endpoint - use `cronjob/v1beta1`(default).
+* CronJob - using `batch/v2alpha1` endpoint - use `cronjob/v2alpha1` (deprecated).
 
 Additionally, if you didn't specify a generator flag, other flags will suggest using
 a specific generator.  Below table shows which flags force using specific generators,