Remove Mambaforge download links

On the [download site](https://conda-forge.org/miniforge/), the first download links the user sees are Mambaforge download links. However, [Mambaforge is deprecated](https://conda-forge.org/news/2024/07/29/sunsetting-mambaforge/), so the Mambaforge download links should be removed or made less visible. Additionally, since [conda-forge's pypy support is deprecated](https://conda-forge.org/news/2024/08/14/sunsetting-pypy/), the Miniforge-pypy3 download links should also be made less visible. If we keep those download links on the page, we should add a note that they are deprecated. Perhaps they could be hidden under a collapsible element like the download links for older versions are.