[truffle] Remove unused attribute

Author: pmurias

src/vm/jvm/runtime/org/perl6/nqp/truffle/nodes/sixmodel/NQPAttributeGetNode.java

@@ -25,8 +25,6 @@
 
 // TODO: take classHandle into account
 public abstract class NQPAttributeGetNode extends NQPObjNode {
-    @Child private NQPNode classHandleNode;
-
     protected abstract String getName();
 
     @Deserializer("attribute-get")