Post plant-animal piping check that the flows to litter from plant reproductive tissues have been reinstated

[jacobcook1995]

There are currently no flows from the plant reproductive tissues to the litter model. This is because most of these flows should really go via the animal model, so needs to wait for the full plant-animal piping to be complete

This issue is a reminder to myself that I need to check up on this once the piping is sorted

[jacobcook1995]

This also includes the relevant inputs from the sub-canopy vegetation (i.e. subcanopy_seedbank_litter_cnp)