BE: Unwrap features from `group_level_security_policies` FF

Why are we doing this work

The backend work for this feature should have never been behind a feature flag; see https://gitlab.com/gl-retrospectives/protect/-/issues/23#note_931198400.

This issue will remove the FF wrapper from the BE code for this feature.

Relevant links

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

• backend remove usage of group_level_security_policies feature flag from GraphQL API

Verification steps