Re-enable rustpython in configs

I've bumped the branch it builds from, so it now builds successfully. If there are ever any issues, please feel free to ping me somewhere - either here, or just open an issue in the RustPython github repository. Or, if there's a better way to do this (pinning to commits in the recipe, maybe?) I'm not particularly attached to the redox-release branch method. I'm hoping to have our regression tests running on redox soon, so there'll be a better chance that any given commit on main will be good on redox.