Fixed: Typo

modules/nix-settings.nix

@@ -1,4 +1,4 @@
-{ pkgs, username, ... }: 
+{ pkgs, username, lib, ... }: 
 {
     # given the users in this list the right to specify additional substituters via:
     #    1. `nixConfig.substituers` in `flake.nix`
@@ -25,7 +25,7 @@
     # do garbage collection weekly to keep disk usage low
     nix.gc = {
         automatic = lib.mkDefault true;
-        dates = lib.mkDefault "1h";
+        dates = lib.mkDefault "1 h";
         options = lib.mkDefault "--delete-older-than +3";
     };