The FetchUserPermissions code for GitLab never had the feature flags added to the context, so the feature flag was not working as intended.

Loom:
https://www.loom.com/share/646c86923b7f4d70ad6e881b67794f6a

Test plan

Tests passing. Added GitLab integration tests to test feature flag.

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    Backport a29b68f from Add feature flags to perms syncer context #56492