demo-image: use empty installCommands for impureMode

wfvm/demo-image.nix

@@ -37,7 +37,10 @@ wfvm.makeWindowsImage {
   # administratorPassword = "12345";
 
   # Imperative installation commands, to be installed incrementally
-  installCommands = with wfvm.layers; [
+  installCommands =
+    if impureMode
+    then []
+    else with wfvm.layers; [
       disable-autosleep disable-autolock disable-firewall
       anaconda3 msys2 msvc msvc-ide-unbreak
     ];