Remove feature flag from Dependency List app

What does this MR do?

Removes the dependency_list_ui feature flag from the Dependency List root application.

Part of Clean up dependency_list_ui feature flag and old code paths.

Related MRs

• !31079 (merged)
• !31096 (merged)
• !31097 (merged)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers