Update contributions.adoc

Corrected mifth forum link.

src/docs/asciidoc/jme3/contributions.adoc

@@ -117,7 +117,7 @@ image::sdk/plugin/glass-shader.png[glass-shader.png,width="150",height="",align=
 |===
 
 a| *Contact person* 
-a| link:http://hub.jmonkeyengine.org/members/mifth/[mifth] 
+a| link:http://hub.jmonkeyengine.org/members/mifth/activity[mifth] 
 
 a| *Documentation* 
 a| <<sdk/plugin/shaderblow#,Wiki Page>>