etc/styles/README: Update copyright year

This has not been getting updated during the bulk copyright year
updates.

etc/styles/README

@@ -1,7 +1,7 @@
 The files OrgOdtContentTemplate.xml and OrgOdtStyles.xml have the
 following copyright information:
 
-Copyright (C) 2010-2014 Free Software Foundation, Inc.
+Copyright (C) 2010-2017 Free Software Foundation, Inc.
 
 These files are part of GNU Emacs.