Clean unnecessary 'attachToDocument' in 'spec/frontend/registry'

Summary

As described in &2419 (closed), we need to clean up our Jest tests from unnecessary attachToDocument usage

Risks

No risks

Involved specs

• spec/frontend/registry/list/components/app_spec.js
• spec/frontend/registry/list/components/collapsible_container_spec.js
• spec/frontend/registry/list/components/project_empty_state_spec.js
• spec/frontend/registry/list/components/table_registry_spec.js