[heap] Remove unused method in ArrayBufferSweeper

Change-Id: I51f2152d8a26fb0b266a41f7d284ced7908eb475
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2554603
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Auto-Submit: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71338}

src/heap/array-buffer-sweeper.h

@@ -103,7 +103,6 @@ class ArrayBufferSweeper {
   void DecrementExternalMemoryCounters();
   void IncrementExternalMemoryCounters(size_t bytes);
   void IncrementFreedBytes(size_t bytes);
-  void IncrementFreedYoungBytes(size_t bytes);
 
   void RequestSweep(SweepingScope sweeping_task);
   void Prepare(SweepingScope sweeping_task);