Remove LoKiGen dependency
LoKiGen is being moved from LHCb to Gauss. See Gauss!664 (closed) and LHCb!2871 (merged). The HepMC record is no longer written. Dependencies in Analysis on HepMC and LoKiGen are to be removed.
No merge request yet, as the starting point depends on whether !709 (closed) can be merged or not.