Javadoc: removed support for JBoss AS 5's VFS

Since Spring 4.0, the VfsUtils class does not support any more the VFS 2 of JBoss AS 5 and JBoss 5.x EAP.
See commit https://github.com/spring-projects/spring-framework/commit/ca194261a42a0a4f0c8bdc36f447e1029a7d2e3e