Hide read_registry scope when registry is disabled on instance

What does this MR do?

Hides the read_registry scope when the internal registry is not enabled

Are there points in the code the reviewer needs to double check?

Is there a better way to code the spec changes without doing the load? The actual fix here is clean and straightforward, but these spec changes make it feel like a hack. Eager to hear feedback here. Thanks!

Why was this MR needed?

We don't have the registry enabled on our instance. I think showing the read_registry option in this case is confusing to users.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• 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
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?