Simplify AlertDialog positive button by using null handler

Co-authored-by: kirklandsign <107070759+kirklandsign@users.noreply.github.com>

Author: Copilot

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/MainActivity.java

@@ -458,11 +458,7 @@ private void askUserToSelectModel() {
               .setTitle("No Model Selected")
               .setMessage(
                   "Please select a model and tokenizer from the settings (top right corner) to get started.")
-              .setPositiveButton(
-                  android.R.string.ok,
-                  (dialog, which) -> {
-                    dialog.dismiss();
-                  })
+              .setPositiveButton(android.R.string.ok, null)
               .show();
         });
   }