Fix removal of pkg_resources

When running tests:

logan/tool.py:19
  /Users/rjw57/projects/uis/devops/tools/logan/logan/tool.py:19: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    import pkg_resources

As of April 2024, this now causes actual breakage for logan:

$ logan --workspace=default terraform init
Traceback (most recent call last):
  File "/Users/rjw57/.local/bin/logan", line 5, in <module>
    from logan.tool import main
  File "/Users/rjw57/.local/pipx/venvs/logan/lib/python3.10/site-packages/logan/tool.py", line 19, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'