storage.conf-freebsd: fix typo

[eriksjolund]

This fix will match how it's written elsewhere

$ git grep  "Auto-userns-max-size is the maximum size" main
main:storage/docs/containers-storage.conf.5.md:  Auto-userns-max-size is the maximum size for a user namespace created automatically.
main:storage/storage.conf:# Auto-userns-max-size is the maximum size for a user namespace created automatically.

[Luap99]

If we have a "duplicated" file for freebsd then I am not sure why it would document the userns size at all , there is no things such as user namespaces there AFAIK so it feels confusing to mention such things in the comments.

[Luap99]

LGTM

I am cool merging this but I think here and in the other repos we could really need a proper doc build system where where can have platform specific bits without duplicating entire files. Not just for the config file but the man pages as well of course.

Anyhow that is much larger topic I guess.

[mtrmac]

Yes, that option seems not to be used in non-Linux.

Either way, this is a clear improvement. Thanks!