Fix units in manage_xyz.write_std_multixyz

[joshkamm]

The unit conversion E*units.KJ_MOL_TO_AU should be E*units.KCAL_MOL_TO_AU
Write some test to double check this.

• In Pycosa, go into the pyproject.toml and lock the pyGSM version to a specific git commit so that this doesn't break pycosa's reverse handling of the issue

[alxstan]

I subscribe to this. Please fix this unit error so that the relative energies in the resulting xyz files are real Hartrees.