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

test/unittests/compiler/graph-unittest.h

Index: test/unittests/compiler/graph-unittest.h
diff --git a/test/unittests/compiler/graph-unittest.h b/test/unittests/compiler/graph-unittest.h
index 2318fa61f83c5d47419da729859fe478155a62fb..9c99992511b828c11f205ff183829c32d95c39aa 100644
--- a/test/unittests/compiler/graph-unittest.h
+++ b/test/unittests/compiler/graph-unittest.h
@@ -18,8 +18,6 @@ namespace internal {
 template <class T>
 class Handle;
 class HeapObject;
-template <class T>
-class Unique;
 
 namespace compiler {
 
@@ -45,7 +43,6 @@ class GraphTest : public TestWithContext, public TestWithIsolateAndZone {
   Node* Int64Constant(int64_t value);
   Node* NumberConstant(volatile double value);
   Node* HeapConstant(const Handle<HeapObject>& value);
-  Node* HeapConstant(const Unique<HeapObject>& value);
   Node* FalseConstant();
   Node* TrueConstant();
   Node* UndefinedConstant();