redirect mypy-lang to mypy on PyPI

[graingert]

took a little while to find the 0.501 release, because it was moved to mypy on PyPI.

It would make my life easier if the long_description of the mypy-lang PyPI entry was just a big <h1> link to https://pypi.org/project/mypy/

[graingert]

And maybe add packages that on install print out the new package location.

[emmatyping]

I think this would be ok if we bump the major version in mypy-lang with an empty package that fails to install (so we don't leave cruft) and just give a notice it moved.

[graingert]

I believe there's a spec for deprecated packages somewhere

[msullivan]

Well we never did this but it has been years and I think it is pretty well-established as the package being mypy, so I'm just gonna close this...