Fix forum link

_config.yml

@@ -23,7 +23,7 @@ project: spring-security
 github_repo_url: http://github.com/spring-projects/spring-security
 
 # Project forum URL
-forum: http://forum.spring.io/spring-projects/security
+forum: http://forum.spring.io/forum/spring-projects/security
 
 # Custom properties
 guides_base_url: http://docs.spring.io/spring-security/site/docs/3.2.x/guides