removes double swap of truth coordinates before writing to file

[krwood]

larnd-sim uses a different internal coordinate system than edep-sim.

Below shows the previous results for truth information (red) and reconstructed hit location (blue). Beam is supposed to be ~ in the z-direction, which suggested that the truth information was not being swapped properly.

[YifanC]

@mjkramer I think they are currently filled at the end because vertices and light_dat are filled during the simulation... Not a very strong reason though