Merge pull request #30958 from lojies/addvalidresourceforexplain

Automatic merge from submit-queue

add valid resources when args is nil

add valid resources message is more friendly to user when running `kubectl explain`
and this also can be same with other cmd like get\describe.

pkg/kubectl/cmd/cmd.go

@@ -245,7 +245,7 @@ Find more information at https://github.com/kubernetes/kubernetes.`,
 			Message: "Basic Commands (Intermediate):",
 			Commands: []*cobra.Command{
 				NewCmdGet(f, out, err),
-				NewCmdExplain(f, out),
+				NewCmdExplain(f, out, err),
 				NewCmdEdit(f, out, err),
 				NewCmdDelete(f, out),
 			},