Remove references to ActionDispatch::IllegalStateError

We were getting a warning after upgrading to Rails 7.1:

```
DEPRECATION WARNING: ActionDispatch::IllegalStateError is deprecated
without replacement.
```

spec/controllers/polls/answers_controller_spec.rb

@@ -13,7 +13,7 @@ describe Polls::AnswersController do
             option_id: question.question_options.find_by(title: "Answer A").id,
             format: :js
           }
-        rescue ActionDispatch::IllegalStateError, ActiveRecord::RecordInvalid
+        rescue ActiveRecord::RecordInvalid
         end
       end.each(&:join)