Update importlib-metadata to 6.0.0

[pyup-bot]

This PR updates importlib-metadata from 1.7.0 to 6.0.0.

Changelog

2.0.0

======

* ``importlib_metadata`` no longer presents a
``__version__`` attribute. Consumers wishing to
resolve the version of the package should query it
directly with
``importlib_metadata.version('importlib-metadata')``.
Closes 71.

Links

• PyPI: https://pypi.org/project/importlib-metadata
• Changelog: https://pyup.io/changelogs/importlib-metadata/
• Repo: https://github.com/python/importlib_metadata

[pyup-bot]

Closing this in favor of #134