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

src/compiler/js-graph.h

Index: src/compiler/js-graph.h
diff --git a/src/compiler/js-graph.h b/src/compiler/js-graph.h
index c7f07d46db9b7827b7cf5b96133f47998e263788..a22a93f4f703567f6855bffa959e490241cba5fb 100644
--- a/src/compiler/js-graph.h
+++ b/src/compiler/js-graph.h
@@ -45,10 +45,6 @@ class JSGraph : public ZoneObject {
   Node* OneConstant();
   Node* NaNConstant();
 
-  // Creates a HeapConstant node, possibly canonicalized, without inspecting the
-  // object.
-  Node* HeapConstant(Unique<HeapObject> value);
-
   // Creates a HeapConstant node, possibly canonicalized, and may access the
   // heap to inspect the object.
   Node* HeapConstant(Handle<HeapObject> value);