[api] Remove marking persistents as partially dependent

src/global-handles.h

Index: src/global-handles.h
diff --git a/src/global-handles.h b/src/global-handles.h
index 24a2273e36d584e50043e7a4d8acc31a6efe51b6..50e5ed6969b0f9a8a113fb4fe62bc48335890c18 100644
--- a/src/global-handles.h
+++ b/src/global-handles.h
@@ -167,9 +167,6 @@ class GlobalHandles {
   // Mark the reference to this object independent of any object group.
   static void MarkIndependent(Object** location);
 
-  // Mark the reference to this object externaly unreachable.
-  static void MarkPartiallyDependent(Object** location);
-
   static bool IsIndependent(Object** location);
 
   // Tells whether global handle is near death.