Fix failing CI due to broken BoltzTraP2 install

[janosh]

I commented out BoltzTraP2 in setup.py util broken install is fixed, hopefully following merge of https://gitlab.com/sousaw/BoltzTraP2/-/merge_requests/18.

Pinging @esoteric-ephemera who helped troubleshoot this issue.

Install logs

Collecting BoltzTraP2>=22.3.2 (from pymatgen==2023.12.18)
  Downloading BoltzTraP2-22.12.1.tar.gz (81.8 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 81.8/81.8 MB 44.5 MB/s eta 0:00:00
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'error'
  error: subprocess-exited-with-error
  
  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [20 lines of output]
      Traceback (most recent call last):
        File "/opt/hostedtoolcache/Python/3.11.7/x64/lib/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
          main()
        File "/opt/hostedtoolcache/Python/3.11.7/x64/lib/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/opt/hostedtoolcache/Python/3.11.7/x64/lib/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
          return hook(config_settings)
                 ^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-lb3tejv2/overlay/lib/python3.11/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=['wheel'])
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-lb3tejv2/overlay/lib/python3.11/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
          self.run_setup()
        File "/tmp/pip-build-env-lb3tejv2/overlay/lib/python3.11/site-packages/setuptools/build_meta.py", line 480, in run_setup
          super(_BuildMetaLegacyBackend, self).run_setup(setup_script=setup_script)
        File "/tmp/pip-build-env-lb3tejv2/overlay/lib/python3.11/site-packages/setuptools/build_meta.py", line 311, in run_setup
          exec(code, locals())
        File "<string>", line 41, in <module>
      ModuleNotFoundError: No module named 'packaging'
      [end of output]