Sort `mdbook` redirects

[mgeisler]

There were a few comments, but I think it’s better to make it all uniform and avoid these comments. The comment was about the v2 rewrite, but this is now done and so the comment is less useful.

I also normalized the quotes to double-quotes instead of single-quotes. The latter is a literal string in TOML, but we don’t actually have any special characters to escape here.