[Ban AI] Remove Feature Flags for Group, Admin, and Project Duo Settings

Context

We need to remove the following feature flags from the codebase when they have been rolled out 100%:

• ai_settings_vue_admin
• ai_settings_vue_group
• ai_settings_vue_project

Associated MRs:

• Ban AI remove Duo Admin Settings FF
• Ban AI remove Duo Group Settings FF
• Ban AI remove Duo Project Settings FF merged ✅

Scope of this issue

• Remove ai_settings_vue_admin feature flag, and references in associated components/specs
• Remove ai_settings_vue_group feature flag, and references in associated components/specs
• Remove ai_settings_vue_project feature flag, and references in associated components/specs