switch back to free HP sane scanner backend, as the proprietary also didn't help with WLAN scanning

nixos/configuration.nix

@@ -114,12 +114,15 @@ in {
       drivers = [ pkgs.hplip ];
     };
   # scanners
-  hardware.sane = 
-    { enable = true;
-      extraBackends = [ pkgs.hplipWithPlugin ];
+  hardware.sane =
+    {
+      enable = true;
+      extraBackends = [ pkgs.hplip ];
     };
-  nixpkgs.config.allowUnfreePredicate = (pkg:
-    pkg.name == pkgs.hplipWithPlugin.name );
+  #  nixpkgs.config.allowUnfreePredicate = (
+  #    pkg:
+  #      pkg.name == pkgs.hplipWithPlugin.name
+  #  );
 
   # Enable sound.
   sound.enable = true;