authors: remove 3rd party lib authors

we do not include the source code of these libs any more.

Author: ThomasWaldmann

AUTHORS

@@ -44,27 +44,3 @@ Attic Patches and Suggestions
 - Johann Klähn
 - Petros Moisiadis
 - Thomas Waldmann
-
-BLAKE2
-------
-
-Borg includes BLAKE2: Copyright 2012, Samuel Neves <[email protected]>, licensed under the terms
-of the CC0, the OpenSSL Licence, or the Apache Public License 2.0.
-
-Slicing CRC32
--------------
-
-Borg includes a fast slice-by-8 implementation of CRC32, Copyright 2011-2015 Stephan Brumme,
-licensed under the terms of a zlib license. See http://create.stephan-brumme.com/crc32/
-
-Folding CRC32
--------------
-
-Borg includes an extremely fast folding implementation of CRC32, Copyright 2013 Intel Corporation,
-licensed under the terms of the zlib license.
-
-xxHash
-------
-
-XXH64, a fast non-cryptographic hash algorithm. Copyright 2012-2016 Yann Collet,
-licensed under a BSD 2-clause license.