Fix groups specs with super sidebar enabled

What does this MR do and why?

Updates a few groups-related specs to pass when the super sidebar is enabled.

Screenshots or screen recordings

No visual change.

How to set up and validate locally

bundle exec rspec spec/features/groups/container_registry_spec.rb
bundle exec rspec spec/features/groups/dependency_proxy_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #420121 (closed)