[shared-struct] Fix isolate creation for testing snapshot

Bug: v8:12547
Change-Id: I32898a4382397663967d7e784e16d7930f3600a2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3859097
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82760}

src/snapshot/snapshot.cc

@@ -346,9 +346,6 @@ void Snapshot::SerializeDeserializeAndVerifyForTesting(
     new_isolate->Enter();
     new_isolate->set_snapshot_blob(&serialized_data);
     new_isolate->set_array_buffer_allocator(array_buffer_allocator.get());
-    if (Isolate* shared_isolate = isolate->shared_isolate()) {
-      new_isolate->set_shared_isolate(shared_isolate);
-    }
     CHECK(Snapshot::Initialize(new_isolate));
 
     HandleScope scope(new_isolate);