Bump pallets-sphinx-themes from 1.2.3 to 2.0.0

Bumps [pallets-sphinx-themes](https://github.com/pallets/pallets-sphinx-themes) from 1.2.3 to 2.0.0.
- [Release notes](https://github.com/pallets/pallets-sphinx-themes/releases)
- [Changelog](https://github.com/pallets/pallets-sphinx-themes/blob/main/CHANGES.rst)
- [Commits](https://github.com/pallets/pallets-sphinx-themes/compare/1.2.3...2.0.0

)

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