Fix backoffLimit field misplacement (#6042)

It should be placed in JobSpec according to:
https://github.com/kubernetes/kubernetes/blob/master/api/swagger-spec/batch_v1.json#L1488-L1514

docs/concepts/workloads/controllers/jobs-run-to-completion.md

@@ -199,7 +199,7 @@ multiple pods running at once.  Therefore, your pods must also be tolerant of co
 ### Pod Backoff failure policy
 
 There are situations where you want to fail a Job after some amount of retries due to a logical error in configuration etc.
-To do so set `.spec.template.spec.backoffLimit` to specify the number of retries before considering a Job as failed.
+To do so set `.spec.backoffLimit` to specify the number of retries before considering a Job as failed.
 The back-off limit is set by default to 6. Failed Pods associated with the Job are recreated by the Job controller with an exponential back-off delay (10s, 20s, 40s ...) capped at six minutes, The back-off limit is reset if no new failed Pods appear before the Job's next status check.
 
 ## Job Termination and Cleanup
@@ -226,6 +226,7 @@ kind: Job
 metadata:
   name: pi-with-timeout
 spec:
+  backoffLimit: 5
   activeDeadlineSeconds: 100
   template:
     metadata:
@@ -236,7 +237,6 @@ spec:
         image: perl
         command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
       restartPolicy: Never
-      backoffLimit: 5
 ```
 
 Note that both the Job Spec and the Pod Template Spec within the Job have a field with the same name.