Readd aims magnetism test

[tpurcell90]

Summary

The aims magnetism test should now work.

Checklist

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• Tests have been added for any new functionality or bug fixes.
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[tpurcell90]

This can merge in once the pymatgen update is possible

[JaGeo]

Yeah. Should hopefully be possible soon. OpenMM tests behave weird again. Will try to fix them and then see....

[tpurcell90]

No rush, I was just checking to see if that was the fail point on here since the test pass locally.