[x/tour] gotour: update Chinese translation link label

"普通话" is a standard Chinese pronunciation, not include Chinese character.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/38310044
X-Tour-Commit: e386ad7d05e604a3433d10e702878f0cbc9a7cbe

tour/content/tour.article

@@ -52,7 +52,7 @@ The tour is available in other languages:
 - [[http://go-tour-kr.appspot.com/][Korean — 한국어]]
 - [[http://go-tour-ro.appspot.com/][Romanian - Română]]
 - [[http://tur.golang.org.tr/][Turkish - Türkçe]]
-- [[http://go-tour-zh.appspot.com/][Chinese — 普通话]]
+- [[http://go-tour-zh.appspot.com/][Chinese — 简体中文]]
 
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