fixed COMPILATION ERROR

 - queueLengthSnapshot never used.

core/src/main/java/hudson/slaves/NodeProvisioner.java

@@ -345,10 +345,6 @@ public class NodeProvisioner {
          * The label under consideration.
          */
         private final Label label;
-        /**
-         * The number of items in the queue requiring this {@link #label}.
-         */
-        private final int queueLengthSnapshot;
         /**
          * The planned capacity for this {@link #label}.
          */