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/officing/voters_controller_spec.rb

@@ -15,7 +15,7 @@ describe Officing::VotersController do
             voter: { poll_id: poll.id, user_id: user.id },
             format: :js
           }
-        rescue ActionDispatch::IllegalStateError, ActiveRecord::RecordInvalid
+        rescue ActiveRecord::RecordInvalid
         end
       end.each(&:join)
 

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)