Disable system,nix updates from Topgrade (#29)

Topgrade is upgrading from local instead of remote, and throws an error
when it tries to upgrade nix. Disabling these checks.

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

users/alice/home.nix

@@ -23,9 +23,8 @@
     # '')
 
     ncdu
-    
+
     # Rust packages
-    topgrade
     trunk
     wasm-pack
     cargo-watch
@@ -59,6 +58,13 @@
       enable = true;
       enableZshIntegration = true;
     };
+
+    topgrade = {
+      enable = true;
+      settings.config = {
+        disable = [ "system" "nix" ];
+      };
+    };
   };
 
   home.stateVersion = "23.11";