Remove FF allow_duo_base_access from frontend

What does this MR do and why?

After the rollout of the FF we want to remove the usage from the frontend.

References

Rollout issue https://gitlab.com/gitlab-org/gitlab/-/issues/536311+

Blocks the cleanup of the backend Remove FF allow_duo_base_access from backend (!191514 - merged)

Screenshots or screen recordings

		Feature
Self-Managed	http://localhost:3000/admin/gitlab_duo
	http://localhost:3000/admin/gitlab_duo/configuration
	http://localhost:3000/groups/group2/-/edit
	http://localhost:3000/groups/group2/subgroup2/-/edit
GitLab.com	http://localhost:3000/groups/group2/-/settings/gitlab_duo
	http://localhost:3000/groups/group2/-/settings/gitlab_duo/configuration
	http://localhost:3000/groups/group2/subgroup2/-/edit

How to set up and validate locally

1. No feature flags are needed.

2. Get a Self-Managed Ultimate license

3. Get an Ultimate license for a group.

4. Include a Duo Enterprise add-on in your subscription or manually create a purchase for your GitLab instance.

   GitlabSubscriptions::AddOnPurchase.create!(subscription_add_on_id: GitlabSubscriptions::AddOn.duo_enterprise.first.id, namespace_id: 165, quantity: 1000, expires_on: 1.year.from_now, started_at: 1.year.ago, organization_id: 1, purchase_xid: "A-S2", trial: false)

5. Ensure Duo Enterprise and Duo Core is displayed according to the screenshots above.

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.

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/544848