Remove wheel from trusted-users

We don't need to use any trusted-users special privileges in daily nix
work, and escalating privileges can be done via sudo

modules/nix-settings.nix

@@ -10,8 +10,6 @@
       "flakes"
     ];
 
-    trusted-users = [ "@wheel" ];
-
     # RPi builds can be slow due to compiling via binfmt.
     download-buffer-size = 1 * 1024 * 1024 * 1024;
   };