add missing license headers (#1809)

command.go

@@ -1,9 +1,10 @@
-// Copyright © 2013 Steve Francia <spf@spf13.com>.
+// Copyright 2013-2022 The Cobra Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
-// http://www.apache.org/licenses/LICENSE-2.0
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,