updated Mercurial's URL

Author: aollier

book/09-git-and-other-scms/sections/client-hg.asc

@@ -34,7 +34,7 @@ $ pip install mercurial
 (If you don't have Python installed, visit https://www.python.org/[] and get it first.)
 
 The last thing you'll need is the Mercurial client.
-Go to http://mercurial.selenic.com/[] and install it if you haven't already.
+Go to https://www.mercurial-scm.org/[] and install it if you haven't already.
 
 Now you're ready to rock.
 All you need is a Mercurial repository you can push to.