[runtime] Remove an unused variable

Bug: v8:11692
Change-Id: I89cdb3d7102123f63fc66106c35962d0578222c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2851878
Auto-Submit: Georg Neis <neis@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74205}

src/runtime/runtime-classes.cc

@@ -188,7 +188,6 @@ Object GetMethodWithSharedName(
 template <typename Dictionary>
 Handle<Dictionary> ShallowCopyDictionaryTemplate(
     Isolate* isolate, Handle<Dictionary> dictionary_template) {
-  Handle<Map> dictionary_map(dictionary_template->map(), isolate);
   Handle<Dictionary> dictionary =
       Dictionary::ShallowCopy(isolate, dictionary_template);
   // Clone all AccessorPairs in the dictionary.