Cannot enable confidential comments events for group webhooks

Summary

When trying to create a new webhook or update an existing one, selecting the "confidential comments" trigger does not work (you can select it, but after saving it does not persist).

/cc @rymai

Steps to reproduce

Try and create a new webhook or update an existing one with the "confidential comments" trigger checked.

Example Project

What is the current bug behavior?

The trigger cannot be enabled

What is the expected correct behavior?

The trigger can be enabled

Relevant logs and/or screenshots

Screen_Recording_2023-03-01_at_09.16.31

Output of checks

Results of GitLab environment info

Results of GitLab application Check

Possible fixes