Update rwfolder.go

Revert copyright/grammar changes.

lib/model/rwfolder.go

@@ -1,8 +1,8 @@
-// Copyright (C) 2015 The Syncthing Authors.
+// Copyright (C) 2014 The Syncthing Authors.
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
-// you can obtain one at http://mozilla.org/MPL/2.0/.
+// You can obtain one at http://mozilla.org/MPL/2.0/.
 
 package model