Typo fix: control plan->control plane

cmd/kubeadm/app/cmd/alpha/certs.go

@@ -40,7 +40,7 @@ var (
     Extra attributes such as SANs will be based on the existing certificates, there is no need to resupply them.
 `)
 	allLongDesc = normalizer.LongDesc(`
-    Renews all known certificates necessary to run the control plan. Renewals are run unconditionally, regardless
+    Renews all known certificates necessary to run the control plane. Renewals are run unconditionally, regardless
     of expiration date. Renewals can also be run individually for more control.
 `)
 )