Field updates does not trigger webhook for transitions with custom event

Summary

Field updates does not trigger webhook for transitions with custom event.

Steps to Reproduce

1. Create a custom event
2. Create a webhook that triggers on Issue Updated event
3. Edit the workflow transition and configure a screen that can update fields.
4. Edit the transition's post function to fire the custom event instead of the generic event.
5. Publish the workflow
6. Use the transition and edit some fields on the screen

Expected Results

JIRA should still catch that the fields (via the transition screen) was updated and trigger the webhook.

Actual Results

The custom event is fired and JIRA webhook is not able to catch that the fields were updated.