Download from Windows 'latest' symlink

Relies on jenkinsci/packaging#188 and needs a
new weekly build before the symlink will actually be updated. Currently
the link points to Jenkins 2.233.

content/download/thank-you-downloading-windows-installer.html.haml

@@ -3,4 +3,4 @@
 :title: Thank you for downloading Windows installer
 ---
 
-= partial('thank-you-downloading-windows-installer.html.haml', :release_url => 'http://mirrors.jenkins-ci.org/windows/2.233/jenkins.msi')
+= partial('thank-you-downloading-windows-installer.html.haml', :release_url => 'http://mirrors.jenkins-ci.org/windows/latest')