BUG: clark_thermalcond is NULL in elastic tensor workflow

[computron]

Describe the bug
If you run the elastic tensor workflow, most things are OK except clark_thermalcond which appears to always be null.

A test workflow is attached
ff_elastic.py

@hrushikesh-s can you look into this? Is it a simple fix?

[hrushikesh-s]

Yes, it's a simple fix. There was a mismatch in the name used for the "Clarke Thermal Conductivity" key in pymatgen & atomate2's schema.
Issue is now fixed in this PR.