nix: Remove fallback for deamon nice levels

modules/nix.nix

@@ -64,15 +64,11 @@ in
       keep-outputs = true
       keep-derivations = true
     '';
-  } // (if (builtins.compareVersions config.system.nixos.release "21.11" != -1) then {
+
     # Make nix build in background less noticeable
     daemonCPUSchedPolicy = "batch";
     daemonIOSchedPriority = 5; # 0-7
-  } else {
-    # TODO 21.11: remove
-    daemonNiceLevel = 10;
-    daemonIONiceLevel = 5; # 0-7
-  });
+  };
 
   nixpkgs.overlays = with inputs; [
     self.overlay