Hello,

Now guile-ssh is required to compile GNU Guix (at least on
core-updates), but it's not specified in
https://git.savannah.gnu.org/cgit/guix.git/tree/README?h=core-updates

I suggest it gets added to avoid confusion to people who compile GNU
Guix without having GNU Guix already and having the ability to run `guix
environment guix`.

Thank you