[HANDS-ON BUG] DuckDuckGoSearchTool use in smolagents notebook fails

**Describe the bug**
When running the code in [Building Agents That Use Code](https://huggingface.co/learn/agents-course/unit2/smolagents/code_agents), the DuckDuckGo search tool is no longer included in the default smolagents package.

**To Reproduce**
Run the code in the [notebook](https://huggingface.co/agents-course/notebooks/blob/main/unit2/smolagents/code_agents.ipynb). The failure happens in the third code block.

**Additional context**
It appears that the DuckDuckGoSearchTool was removed as a required dependency in smolagents [v1.15.0](https://github.com/huggingface/smolagents/releases/tag/v1.15.0), and was replaced in the documentation with WebSearchTool.
Remember to update the course pages and not just the notebook.