[heap] Remove ObjectMarking::ClearMarkBit.

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 1439118719634c2a96c7a6b4eaa0c67c3804b8cc..254748174fdfd3f1c1210b9bd8345f1b01c3c71a 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -73,11 +73,6 @@ class ObjectMarking : public AllStatic {
   }
 
   template <MarkingMode mode = MarkingMode::FULL>
-  V8_INLINE static void ClearMarkBit(HeapObject* obj) {
-    Marking::MarkWhite(MarkBitFrom<mode>(obj));
-  }
-
-  template <MarkingMode mode = MarkingMode::FULL>
   V8_INLINE static void BlackToGrey(HeapObject* obj) {
     DCHECK(IsBlack<mode>(obj));
     MarkBit markbit = MarkBitFrom<mode>(obj);