[turbofan] Remove usage of Unique<T> from graph.

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index 50a94342c9abb97e16f853f79747615a3fb5d951..e22f5458697b852f59300dc5e4011298673da45e 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -183,7 +183,7 @@ class OperandGenerator {
       case IrOpcode::kExternalConstant:
         return Constant(OpParameter<ExternalReference>(node));
       case IrOpcode::kHeapConstant:
-        return Constant(OpParameter<Unique<HeapObject> >(node).handle());
+        return Constant(OpParameter<Handle<HeapObject>>(node));
       default:
         break;
     }