message: Use absl::optional instead of std::optional
diff: @@ -1520,7 +1520,7 @@ PjRtExecutable::MakeExecutionInputsAndWaitForEvents(
  LocalDeviceState* device_state = &client_->device_state(device_ordinal);
  // Lift tuple_handle outside the conditional so that the event it returns is
  // not destroyed until after the loop below that waits on events.
  - std::optional<TupleHandle> tuple_handle;
  + absl::optional<TupleHandle> tuple_handle;
  if (parameter_is_tupled_arguments_ && !options.arguments_are_tupled) {
  TF_ASSIGN_OR_RETURN(tuple_handle,
  MakeTupleHelper(client_, device_state, argument_handles,
  