docs(licence): update licence dates

setup.py

 #!/usr/bin/env python
 # pylint: disable=W0142,W0403,W0404,W0613,W0622,W0622,W0704,R0904,C0103,E0611
 #
-# copyright 2003-2016 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# copyright 2003-2021 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
 # contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
 #
 # This file is part of a CubicWeb cube.