`fly help machines update` seems wrong about default `autostop` value

[mwcampbell]

If I run fly help machines update, the default value of the autostop flag is listed as true. But that disagrees with the fly.toml documentation, which says that the default value of the corresponding fly.toml flag is false. Also, I have a Fly Postgres machine with no explicit value for autostop, and without the FLY_SCALE_TO_ZERO variable, and the machine doesn't autostop. So apparently the default value of autostop really is false.