lock_version shows up in webhooks

Summary

An internal field is showing up in webhooks.

Steps to reproduce

Receive MR and/or Issue hooks from a project. There's a lock_version field which appears to be an internal DB field of Issuable.

Expected behavior

lock_version shouldn't be in webhooks?

Actual behavior

lock_version appears in the webhooks.

Output of checks

No shell access to the installation.

Possible fixes

Hide hidden fields from hook_attrs.