Broken Tutorial "Beginner: Client libraries" / "Writing a simple service and client (C++)"

[Darkproduct]

The example code for the client doesn't compile.

Example: result is used (L218) before it is declared (L225)

ros2_documentation/source/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Service-And-Client.rst

Lines 218 to 225 in 2f740f5

	if (rclcpp::spin_until_future_complete(node, result) ==
	rclcpp::FutureReturnCode::SUCCESS)
	{
	RCLCPP_ERROR(node->get_logger(), "service call failed :(");
	client->remove_pending_request(result_future);
	return 1;
	}
	auto result = result_future.get();

I think this was somehow messed up in 6e92e0e, which, from the commit message, should only update python tutorials. @clalancette

[fujitatomoya]

@Darkproduct thanks for creating issue, i just made #4917, it would be appreciated if you can review.