Remove all copyright license headers

Discussion previously happened in https://github.com/rust-lang/rust/pull/43498

util/export.py

@@ -1,16 +1,5 @@
 #!/usr/bin/env python
 
-# Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
-# file at the top-level directory of this distribution and at
-# http://rust-lang.org/COPYRIGHT.
-#
-# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-# option. This file may not be copied, modified, or distributed
-# except according to those terms.
-
-
 # Build the gh-pages
 
 import re