Clean up ci_jwt_v2_ref_uri_claim FF

What does this MR do and why?

Clean up ci_jwt_v2_ref_uri_claim feature flag.

FF was added in Add `ci_config_ref_uri` claim to Ci::JwtV2 for ... (!122373 - merged)

Rollout issue: [Feature flag] Rollout of `ci_jwt_v2_ref_uri_cl... (#412926 - closed)

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