winbuild/MakefileBuild.vc: bump copyright year

winbuild/MakefileBuild.vc

@@ -5,7 +5,7 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 1999 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 1999 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms