chore: replace absl::optional<T> with std::optional<T> (#40928)

* chore: replace absl::optional<T> with std::optional<T>

* IWYU

shell/browser/net/node_stream_loader.cc

@@ -59,7 +59,7 @@ void NodeStreamLoader::Start(network::mojom::URLResponseHeadPtr head) {
 
   producer_ = std::make_unique<mojo::DataPipeProducer>(std::move(producer));
   client_->OnReceiveResponse(std::move(head), std::move(consumer),
-                             absl::nullopt);
+                             std::nullopt);
 
   auto weak = weak_factory_.GetWeakPtr();
   On("end",