chore(LICENSE): Refactor header so GitHub's parser recognizes the MIT license

Author: erikmd

LICENSE

@@ -1,9 +1,7 @@
-(c) Copyright 2019 OCaml Software Foundation.
-(c) Copyright 2016-2018 OCamlPro.
+MIT License
 
-Licensed under the MIT license:
-
-    http://www.opensource.org/licenses/mit-license.php
+Copyright (c) 2019  OCaml Software Foundation.
+Copyright (c) 2016-2018  OCamlPro.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal