Seems the `svg` org was shadowbanned by GitHub. Me and other SVGO contributors and maintainers would like to get it back but will have to wait on them. In the meantime you can still access SVGO via `git`, `gh`, and `npm`.
Well umm linking to a private repo isn't much use now is it? You just get the "404 Not Found". So what was SVGO anyway? (never heard of it)