Update packaging to 20.7

[pyup-bot]

This PR updates packaging from 20.4 to 20.7.

Changelog

20.7

~~~~~~~~~~~~~~~~~

No unreleased changes.

20.6

~~~~~~~~~~~~~~~~~

* Fix flit configuration, to include LICENSE files (:issue:`357`)

20.5

~~~~~~~~~~~~~~~~~

* Officially support Python 3.9 (:issue:`343`)
* Deprecate the ``LegacyVersion`` and ``LegacySpecifier`` classes (:issue:`321`)
* Handle ``OSError`` on non-dynamic executables when attempting to resolve
the glibc version string.

Links

• PyPI: https://pypi.org/project/packaging
• Changelog: https://pyup.io/changelogs/packaging/
• Repo: https://github.com/pypa/packaging

[pyup-bot]

Closing this in favor of #39