Remove unused VisitWeakList2 declaration

Bug: v8:10155
Change-Id: Ie58924fdbdb2267ec7d7e3cc63d9cd504fd4f4d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2053079
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66263}

src/heap/objects-visiting.h

@@ -143,8 +143,6 @@ class WeakObjectRetainer;
 // access the next-element pointers.
 template <class T>
 Object VisitWeakList(Heap* heap, Object list, WeakObjectRetainer* retainer);
-template <class T>
-Object VisitWeakList2(Heap* heap, Object list, WeakObjectRetainer* retainer);
 }  // namespace internal
 }  // namespace v8