go-tour: add link to Traditonal Chinese translation
go-tour: add link to Traditonal Chinese translation

LGTM=minux.ma
R=golang-codereviews, minux.ma
CC=golang-codereviews
https://codereview.appspot.com/100100043

Go-zh/tour-old,minux/go-tour-zh,Go-zh/tour-old,minux/go-tour-zh