Resolve "Only show Duo CE UI when beta features are enabled"

What does this MR do and why?

Hides Duo Context Exclusion UI in a project when beta features aren't enabled in the parent group.

How to set up and validate locally

1. Create a project in an ultimate licensed group
2. Enable the feature flag use_duo_context_exclusion for the project
3. Disable Turn on experiment and beta GitLab Duo features checkbox on the group
4. Project settings >> Gitlab Duo should not show Duo Context Exclusion
5. Enable Turn on experiment and beta GitLab Duo features on the group
6. Project settings >> Gitlab Duo should now show Duo Context Exclusion

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #561795 (closed)