FIX: Fix flaky test resulting from PostAlerter keyword arguments (#19826)

We've been doing some work to support new keyword argument semantics in Ruby 3. As part of that we made some changes to `DiscourseEvent::TestHelper`. The backwards compatibility fix doesn't work if the method is called with an empty hash as the final argument. This fix adds a valid option to the final hash in the particular test.

spec/services/post_alerter_spec.rb

@@ -1053,10 +1053,12 @@ RSpec.describe PostAlerter do
     it "triggers :before_create_notification" do
       type = Notification.types[:private_message]
       events =
-        DiscourseEvent.track_events { PostAlerter.new.create_notification(user, type, post, {}) }
+        DiscourseEvent.track_events do
+          PostAlerter.new.create_notification(user, type, post, { revision_number: 1 })
+        end
       expect(events).to include(
         event_name: :before_create_notification,
-        params: [user, type, post, {}],
+        params: [user, type, post, { revision_number: 1 }],
       )
     end
   end