[release-branch.go1.7] doc: remove Reddit as an official space where Code of Conduct applies

Fixes #18289

Change-Id: I047e98cc36b861ef15292170aeaff8bc29243cab
Reviewed-on: https://go-review.googlesource.com/34281Reviewed-by: Russ Cox <rsc@golang.org>
(cherry picked from commit 265e5476)
Reviewed-on: https://go-review.googlesource.com/34282

doc/conduct.html

@@ -67,7 +67,6 @@ official forums operated by the Go project (“Go spaces”):
     <li>The <a href="https://groups.google.com/group/golang-nuts">golang-nuts</a> and
         <a href="https://groups.google.com/group/golang-dev">golang-dev</a> mailing lists.
 <li>The #go-nuts IRC channel on Freenode.
-<li>The <a href="https://reddit.com/r/golang">/r/golang subreddit</a>.
 </ul>
 
 <p>