heap: Fix TracedReference::IsEmptyThreadSafe again

reinterpret_cast to std::atomic was missing const.

Bug: chromium:1108537
Change-Id: Ib737418bddbef6774deafa9714b0efcf2e3fd07c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2332797
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69194}

include/v8.h

@@ -917,7 +917,7 @@ class TracedReferenceBase {
    * Get this reference in a thread-safe way
    */
   const T* GetSlotThreadSafe() const {
-    return reinterpret_cast<std::atomic<const T*>*>(&val_)->load(
+    return reinterpret_cast<std::atomic<const T*> const*>(&val_)->load(
         std::memory_order_relaxed);
   }