Missing settings in push rules

Summary

Some settings are missing from the push rules admin's settings.

When installing my instance; I activated the "Check whether commit is signed through GPG" setting. Today I cant disable it as it is not present as the doc states. See screenshot

Steps to reproduce

I do not know exactly how to reproduce as I cant reproduce on my instance nor on gitlab.com

Relevant logs and/or screenshots

chrome_2018-06-15_13-22-52

Env infos

I'm under GitLab Enterprise Edition 10.8.4-ee f80a5284 (free for open source)