[css-writing-modes] Unicode 6.3 year changed to 2013

Author: kojiishi

biblio.ref

@@ -5592,7 +5592,7 @@
 %L UNICODE
 %A The Unicode Consortium
 %T The Unicode Standard
-%D 2012
+%D 2013
 %O Defined by: The Unicode Standard, Version 6.3.0, (Mountain View, CA: The Unicode Consortium, 2013. ISBN 978-1-936213-08-5), as updated from time to time by the publication of new versions
 %U http://www.unicode.org/standard/versions/enumeratedversions.html