[Hot Fix] Fix setuptools for pymatgen packaging

[DanielYang59]

Summary

• A hot fix for Installation failed using self-forked version #3928, where the setuptools in not configured to include the complete pymatgen package (all subpackages are missing) after moving to the src layout.
• (description is incorrect, see Remove explicit declare of package-data #4018) Turn off include-package-data, which is true by default, meaning package-data is not having any effect and all data files would be included into the package.
• Remove resolved skip tag:

  pymatgen/tests/core/test_structure.py

  Line 1771 in 0234182

  @pytest.mark.skip("TODO remove skip once https://github.com/materialsvirtuallab/matgl/issues/238 is resolved")

Site note

To reliably recreate this issue, one might need to completely clear build cache (removing build/, dist/ and *.egg-info), otherwise you might find yourself (me for example) modifying the pyproject.toml file but find the wheel remains unchanged.

[DanielYang59]

@shyuep @janosh @mkhorton Can you please review this hot fix? Thanks!