Rollback changes made to signing_enabled.

** I advise the reviewer to have the original MR open when reviewing this: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12491/diffs **

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #37202 (closed)