remove somewhat off-topic details about setting up a substituter

Author: tstat

README.md

@@ -85,21 +85,6 @@ use to avoid compiling linux yourself. The cache can be found at
 https://nix-community.cachix.org, and you can follow the instructions there
 to use this cache.
 
-You don't need the cachix binary to use the cachix cache though, you
-just need to add the relevant
-[`substituters`](https://nixos.org/manual/nix/stable/command-ref/conf-file.html?highlight=nix.conf#conf-substituters)
-and
-[`trusted-public-keys`](https://nixos.org/manual/nix/stable/command-ref/conf-file.html?highlight=nix.conf#conf-trusted-public-keys)
-settings settings to your `nix.conf`. You can do this directly by
-modifying your `/etc/nix/nix.conf`, or in the flake definition. In the
-above example flake these `nix.conf` settings are added by the
-`nixConfig` attribute ([doc
-link](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-flake.html?highlight=flake#flake-format)).
-Note that this will only work if the user running `nix build` is in
-[`trusted-users`](https://nixos.org/manual/nix/stable/command-ref/conf-file.html?highlight=nix.conf#conf-trusted-users)
-or the substituter is in
-[`trusted-substituters`](https://nixos.org/manual/nix/stable/command-ref/conf-file.html?highlight=nix.conf#conf-trusted-substituters).
-
 ## Building an sd-card image
 
 An image suitable for flashing to an sd-card can be found at the