RFR: Remove dead process_evacuate_roots() in ShenandoahRootsProcessor

[Roman Kennke]

We've got a dead method in ShenandoahRootProcessor, this one is now in
ShenandoahRootsEvacuator. Ok to remove?

http://cr.openjdk.java.net/~rkennke/deadcode/webrev.00/

Roman