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)

Signed-off-by: dependabot[bot] <support@github.com>

requirements-dev.txt

@@ -7,7 +7,7 @@ splinter==0.14.0
 transifex-client==0.14.2
 selenium==3.141.0
 twine==3.4.1
-Pallets-Sphinx-Themes==1.2.3
+Pallets-Sphinx-Themes==2.0.0
 docutils==0.16
 Sphinx==3.5.4
 sphinx-issues==1.2.0