Change 'recommendations' field type from object to array in APIEnrollment schema

Changes

• Updated endpoints
  • No endpoint URL changes but schema changes for:
    • GET /enrollment/<enrollment_id>/recommendations (implied from PR)
      • The recommendations field in the APIEnrollment schema was changed from an object to an array type.
      • This aligns with the underlying data change from Optional[dict] to Optional[list].

No new or deleted endpoints introduced in this release.