Log Message:
py-pallets-sphinx-themes: updated to 2.1.1

Version 2.1.1
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- Remove leftover Python 2 compatibility code. :pr:`69`
- Dotted underlines on links are smaller. :issue:`70`

Version 2.1.0
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- Drop support for Python 3.6 and 3.7.
- Require Sphinx >= 3.
- Remove previously deprecated code.
- Fix table of contents overflow issue.