build: align minimum build dependencies with ndn-cxx

 * gcc 7.4
 * clang 6.0
 * Xcode 10.0 (11.3 or later recommended)

Change-Id: I85f40520d9b1edda4ebcabcea13570a07e124ad4
diff --git a/docs/conf.py b/docs/conf.py
index e88e6bf..82be059 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -18,7 +18,7 @@
 # -- Project information -----------------------------------------------------
 
 project = u'NAC: Name-based Access Control library'
-copyright = u'Copyright © 2014-2021 Regents of the University of California.'
+copyright = u'Copyright © 2014-2022 Regents of the University of California.'
 author = u'Named Data Networking Project'
 
 # The short X.Y version.