Update to upstream cypython branch

[benbrandt]

Since it seems there is not a need for a branch on your fork, I thought it might be nice to pin instead to one of the version branches in the upstream repository.

Still to do: I think we might need to update the CI cache key to the current commit hash of the submodule.. but I might need to think about how best to do that, and wanted to run the idea of moving to upstream first.

[dicej]

@benbrandt I'd be happy to switch to the upstream repo, but my understanding is that upstream supports neither shared libraries nor TCP/UDP sockets for WASI, hence my patch: dicej/cpython@118e9d8

Until both of those features are available upstream, I think we'll either need to keep pointing at my fork or else check the patch into this repo and apply it as part of the build process.

[benbrandt]

@dicej ah ok I somehow missed where you had that commit in your repo. No worries