[cleanup] Remove unused function in SharedStringAccessGuardIfNeeded

Change-Id: Ifad7bbafc8b7c7ff8cf9140b9227cb9c67370fcf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2637856
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72162}

src/objects/string-inl.h

@@ -62,8 +62,6 @@ class V8_NODISCARD SharedStringAccessGuardIfNeeded {
   }
 #endif
 
-  static bool IsNeeded(Isolate* isolate) { return false; }
-
   static bool IsNeeded(LocalIsolate* local_isolate) {
     // TODO(leszeks): Remove the nullptr check for local_isolate.
     return local_isolate && !local_isolate->heap()->is_main_thread();