spec: we're now at Unicode 6.2.0

R=golang-dev
CC=golang-dev
https://golang.org/cl/6818083

doc/go_spec.html

@@ -5265,7 +5265,7 @@ package and may be relative to a repository of installed packages.
 <p>
 Implementation restriction: A compiler may restrict ImportPaths to
 non-empty strings using only characters belonging to
-<a href="http://www.unicode.org/versions/Unicode6.0.0/">Unicode's</a>
+<a href="http://www.unicode.org/versions/Unicode6.2.0/">Unicode's</a>
 L, M, N, P, and S general categories (the Graphic characters without
 spaces) and may also exclude the characters
 <code>!"#$%&amp;'()*,:;&lt;=&gt;?[\]^`{|}</code>