Invalid link to LLM "Build reasoning models" course page "Advanced understanding of GRPO in DeepSeekMath"

I think the otherwise superb HF LLM course has need for revision in other parts as pointed out in previous issues, but in the section Build reasoning models the page Advanced understanding of GRPO in DeepSeekMath is leading to frank "442 - Unprocessable entity" and missing page.

The url trying to be fetched is 
```https://huggingface.co/learn/llm-course/chapter12/3a```