Merge request "Submit review" and "Re-request review" buttons do not trigger webhook events

Summary

Clicking "Submit review" in the "Finish review" dialog, or the "Re-request review" button on a Merge Request should cause webhook events to be generated. However, they do not generate any webhook events.

Steps to reproduce

1. Create a webhook at the group level of your project. (I have not tested whether project-level webhooks have the same problem.)
   1. Set the URL to point somewhere where you can see all of the requests that come in. (I used a Zapier webhook.)
   2. Enable all triggers
   3. Save the webhook it
2. Create a merge request. Confirm that you see a webhook event.
3. Set a reviewer. Confirm that you see a webhook event.
4. Add a comment to any line of the changes and click "Start a review".
5. Click "Finish review" and select "Request changes" and then "Submit review". No webhook event is generated.
6. In the overview, the "Re-request review" button (A circular arrow) will appear next to the Reviewers field. Click it. No webhook event is generated.

What is the current bug behavior?

Clicking "Submit review" or the "Re-request review" button do not generate webhook events.

What is the expected correct behavior?

Clicking "Submit review" or the "Re-request review" button should generate webhook events.

Relevant logs and/or screenshots

The Finish review dialog.

The Re-request review button.

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Describe what you would like to see improved.