Get rid of VCR.py

[pawelad]

I still very much like the idea of https://github.com/kevin1024/vcrpy, but I think it works best when the API is publicly accessible and doesn't contain any sensitive data.

Right now, I'm using it alongside https://github.com/CarloDePieri/vcrpy-encrypt, but that means the tests can't be run in PRs opened by other people.

Thus, I think I should just migrate the VCR.py tests to use https://github.com/lundberg/respx instead.