More issues with pressure #213

I found a couple more pressure issues --

1. Pressure not properly passed to msgpack:

   tyff/tyff/compute/_produce.py

   Line 141 in 08ad267

   pressure=pressure if pressure is None else openmm.unit.kilopascal,

   This doesn't actually pass the pressure, just the unit itself. Same error in _equilibrate.py .

2. Jacobian computation still assumes atmosphere:

   tyff/tyff/compute/_jacobian.py

   Line 144 in 08ad267

   None if pressure is None else pressure * openmm.unit.atmosphere,

   
   (and there's a comment earlier that also assumes it's in atmosphere:

   tyff/tyff/compute/_jacobian.py

   Line 81 in 08ad267

   pressure = compute_config.get("pressure") # atmosphere, float | None