Removes a vestigial shutdown handler
When opporozidone removes the RottingComponent, the PerishableComponent's
RotNextUpdate is set to 0 - and then it undergoes a period of catch-up to
the current time. If the entity is susceptible to rot in that interval, it'll
accumulate 2 minutes 30 seconds worth of rot, per second.
This gets worse the longer the server has been running, as there's a greater value
in _timing.CurTime to catch up to. This handler seems to be vestigial from the
MiasmaSystem and does not seem to be necessary for anything anymore.
