Add --show-all to documentation

`kubectl get pods -l jobgroup=jobexample --show-all -o name`
will not show the completed jobs.  This caught me when running through the steps myself.

docs/tasks/job/parallel-processing-expansion.md

@@ -99,7 +99,7 @@ There is not a single command to check on the output of all jobs at once,
 but looping over all the pods is pretty easy:
 
 ```shell
-$ for p in $(kubectl get pods -l jobgroup=jobexample -o name)
+$ for p in $(kubectl get pods -l jobgroup=jobexample --show-all -o name)
 do
   kubectl logs $p
 done