remove undetectable strings

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index ef8416ae4382dc27e20774b04232e8f2af4ce28d..fa4e3cedcef9e9d26af3d36710b932eb6457b2cd 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8985,10 +8985,6 @@ class String: public Name {
   // Requires: StringShape(this).IsIndirect() && this->IsFlat()
   inline String* GetUnderlying();
 
-  // Mark the string as an undetectable object. It only applies to
-  // one-byte and two-byte string types.
-  bool MarkAsUndetectable();
-
   // String equality operations.
   inline bool Equals(String* other);
   inline static bool Equals(Handle<String> one, Handle<String> two);