Is called like this since 14321ae2431e33f5ed81f1ee43eddd29c7e9d01d, but
docs were still using the old option in some cases.
Reported-By: Cedric Shahabi <cedric.shahabi@gmail.com>
* improve nix installation instructions
in the command
$ bash <(curl https://nixos.org/nix/install)
<(..) is a bashism. The documentation now show a command that does
not require to be executed by bash.
