fix latest stable tarball link

Author: disfated

downloads.html

@@ -102,7 +102,7 @@ <h2 class="title"><img class="title" src="images/logo-tar.png"/>
 	Source Releases
 </h2><ul>
 <li>
-<a href="{{ site.cola_downloads }}/cola-{{ site.cola_version }}.tar.gz">
+<a href="{{ site.cola_downloads }}/git-cola-{{ site.cola_version }}.tar.gz">
 	git-cola v{{ site.cola_version }}</a> (latest stable release)
 </li>
 <li>