Remove or implement the field "New Issue Url" from custom issue tracker integration page

The "New issue url" that can be added in Settings > Integrations > Custom Issue Tracker is not used anywhere in GitLab and highly misleading to the user. It has also created confusion among GitLab team members building new functionality.

Custom_Issue_Tracker___Integrations___Settings___GitLab_org___security-products___dast___GitLab

The documentation states that:

| New issue URL | Currently unused. Will be changed in a future release. | but this documentation was added two years ago.

The field should be removed, or it should be used in the application.