Cleanup: remove `set_win32_cert_path()` unused function.

[clamoriniere]

From the git history, we can see that this function is not used since 5.12.x.
It was introduce to solve an issue with old tornado version < 3.0.0.

During the cleanup the ca-certificates.crt that is used in this function and package with the win32 build, can be removed too.