doc: remove link to http://golanguage.ru/

I check it for several months and it always says
ERR_NAME_RESOLUTION_FAILED

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5272041

doc/docs.html

@@ -165,11 +165,6 @@ Notable articles from the <a href="http://blog.golang.org/">Go Blog</a>.
 <li><a href="http://code.google.com/p/golang-korea">golang-korea</a> - Go documentation and news.
 </ul>
 
-<h3 id="docs_ru">Russian &mdash; Русский</h3>
-<ul>
-<li><a href="http://golanguage.ru/">golanguage.ru</a> - Go documentation.
-</ul>
-
 </div>