Can we remove the docs folder?

[Arun-Niranjan]

The old docs folder is still available at https://github.com/infer-actively/pymdp/tree/main/docs - I believe this is entirely superseded by the autogenerated docs in https://github.com/infer-actively/pymdp/tree/main/docs-mkdocs

This is confusing for new users, who reasonably from a search engine go straight to the docs folder, which is out of date.

We should remove this docs folder entirely now we have completed the v1 release.