Reorder the footnotes in the banning policy to be in the right order

[Lyroth001]

This has annoyed me for far too long how has it taken anyone this long to get fed up with it

[Lyroth001]

footnote 13 seems unused for whatever reason? so removed that

[PJB3005]

The hell? I thought Markdown footnotes are supposed to automatically order themselves based on first use. Something doesn't add up here, you shouldn't need to re-organize these manually.

[PJB3005]

Yeah updating the version of mdbook we're running actually fixes this. That's probably a better idea.

[Lyroth001]

yeah that would also seem sensible