`spin_some` is deprecated

```
ros2_ws/src/simple_actions/include/simple_actions/simple_client.hpp:151:26: warning: ‘void rclcpp::spin_some(Node::SharedPtr)’ is deprecated: use SingleThreadedExecutor::spin_some instead [-Wdeprecated-declarations]
  151 |         rclcpp::spin_some(node_);
      |         ~~~~~~~~~~~~~~~~~^~~~~~~
```