Use the correct project visibility in system hooks
What does this MR do?
This makes sure the
Project#visbility is used in system webhooks.
Gitlab::VisibilityLevel.string_options which isn't used for translations, rather than
Gitlab::VisibilityLevel.options which includes namespaces for translations.
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Tests added for this feature/bug
- Has been reviewed by Backend