Is anything here actually using the new changes in pythoncapi_compat.h?

There's no reason to stick with an old version, but I'm curious if there is a reason for updating it in what looks like an unrelated PR?

No, upgrading pythoncapi_compat was actually needed in an earlier version of my patch, but I actually ended up not needing the new stuff.

However, I thought that it might be okay for the header to be upgraded anyway, that's why I left it in.