Update an example to use the new LLVM file header.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@351653 91177308-0d34-0410-b5e6-96231b3b80d8

docs/DesignDocs/CapturingConfigInfo.rst

@@ -56,10 +56,9 @@ configuration all together. An example "__config" header generated when
 
   //===----------------------------------------------------------------------===//
   //
-  //                     The LLVM Compiler Infrastructure
-  //
-  // This file is dual licensed under the MIT and the University of Illinois Open
-  // Source Licenses. See LICENSE.TXT for details.
+  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+  // See https://llvm.org/LICENSE.txt for license information.
+  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   //
   //===----------------------------------------------------------------------===//
 
@@ -77,10 +76,9 @@ configuration all together. An example "__config" header generated when
   // -*- C++ -*-
   //===--------------------------- __config ---------------------------------===//
   //
-  //                     The LLVM Compiler Infrastructure
-  //
-  // This file is dual licensed under the MIT and the University of Illinois Open
-  // Source Licenses. See LICENSE.TXT for details.
+  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+  // See https://llvm.org/LICENSE.txt for license information.
+  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   //
   //===----------------------------------------------------------------------===//