change channale/Nix

[saeed@stack ~]$ nix-channel --list
[saeed@stack ~]$ sudo nix-channel --list
unstable https://nixos.org/channels/nixos-unstable
[saeed@stack ~]$ echo $NIX_PATH
nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels