318fba182a
It looks like the last update (https://github.com/NixOS/nixpkgs/pull/176677) got the version number wrong (20210107, but should be 20210117). See https://github.com/MLton/mlton/releases/tag/on-20210117-release that has a similar error in the heading (but not in the URL or links). This corrects this version mismatch. There is no change to the content of the package.