Update to 3.2.2. Upstream changelog:

• Add checklinks tox environment to ensure all links in documentation are good.
• Refactor extension API documentation (#729).
• Load entry_points (for extensions) only once using importlib.metadata.
• Do not double escape entities in TOC.
• Correctly report if an extension raises a TypeError (#939).
• Raise a KeyError when attempting to delete a nonexistent key from the extension registry (#939).
• Remove import of packaging (or pkg_resources fallback) entirely.
• Remove setuptools as a run-time dependency (install_required).