Try installing requirements.txt in workflow

[benlandrum]

Try to fix the following error during the wheel build step of the CI workflow undergoing an update in mpi4py#30.

* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools >= 40.8.0
* Getting build dependencies for sdist...
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.10.14/x64/lib/python3.10/site-packages/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
    main()
  File "/opt/hostedtoolcache/Python/3.10.14/x64/lib/python3.10/site-packages/pyproject_hooks/_in_process/_in_process.py", line 335, in main
    json_out['return_val'] = hook(**hook_input['kwargs'])
  File "/opt/hostedtoolcache/Python/3.10.14/x64/lib/python3.10/site-packages/pyproject_hooks/_in_process/_in_process.py", line 287, in get_requires_for_build_sdist
    return hook(config_settings)
  File "/tmp/build-env-lf1dau7p/lib/python3.10/site-packages/setuptools/build_meta.py", line 328, in get_requires_for_build_sdist
    return self._get_build_requires(config_settings, requirements=[])
  File "/tmp/build-env-lf1dau7p/lib/python3.10/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
    self.run_setup()
  File "/tmp/build-env-lf1dau7p/lib/python3.10/site-packages/setuptools/build_meta.py", line 487, in run_setup
    super().run_setup(setup_script=setup_script)
  File "/tmp/build-env-lf1dau7p/lib/python3.10/site-packages/setuptools/build_meta.py", line 311, in run_setup
    exec(code, locals())
  File "<string>", line [12](https://github.com/benlandrum/mpi4py-fft/actions/runs/8491772884/job/23264065777#step:6:13), in <module>
ModuleNotFoundError: No module named 'numpy'