Bump sphinx-tabs from 2.1.0 to 3.1.0

Bumps [sphinx-tabs](https://github.com/executablebooks/sphinx-tabs) from 2.1.0 to 3.1.0.
- [Release notes](https://github.com/executablebooks/sphinx-tabs/releases)
- [Changelog](https://github.com/executablebooks/sphinx-tabs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/executablebooks/sphinx-tabs/compare/v2.1.0...v3.1.0

)

---
updated-dependencies:
- dependency-name: sphinx-tabs
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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