Update links in the Trebuchet blog post?

[schlichtanders]

The link in the blog-post https://fluxml.ai/2019/03/05/dp-vs-rl.html

Are pointing towards old code https://github.com/FluxML/model-zoo/blob/10bd26ca21079b1c6ee246dd1938beab55178949/games/differentiable-programming/trebuchet/DiffRL.jl

That code is no longer working (packages are no longer in the General registry), and hence it should be pointed to the more current version https://github.com/FluxML/model-zoo/tree/master/contrib/games/differentiable-programming/trebuchet

This would be especially helpful, because as you can see the new link is under contrib/games and hence cannot be found by just switching branches.

At the README.md of Trebuchet.jl there was a similar issue, which was fixed in FluxML/Trebuchet.jl#9