Update entitysystem.adoc

Fixed broken link.

src/docs/asciidoc/jme3/contributions/entitysystem.adoc

@@ -53,6 +53,6 @@ A lot of very up-to-date information on the Zay-ES entity system can be found on
 
 == Zay-ES Download
 
-Zay-ES can be downloaded via SVN from link:https://github.com/jMonkeyEngine-Contributions/zay-es[http://code.google.com/p/jmonkeyplatform-contributions/source/browse/trunk/zay-es/]
+Zay-ES can be downloaded via SVN from link:https://github.com/jMonkeyEngine-Contributions/zay-es[https://github.com/jMonkeyEngine-Contributions/zay-es]
 
 It also now available as a jMonkey SDK plugin.