Bump sphinx-tabs from 1.3.0 to 3.1.0

Bumps [sphinx-tabs](https://github.com/executablebooks/sphinx-tabs) from 1.3.0 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/v1.3.0...v3.1.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -8,7 +8,7 @@ sphinx_rtd_theme==0.5.2
 
 # Code tabs extension for GDScript/C#
 # Stay on 1.3.0 until https://github.com/readthedocs/readthedocs-sphinx-search/issues/82 is fixed.
-sphinx-tabs==1.3.0  # pyup: ignore
+sphinx-tabs==3.1.0  # pyup: ignore
 
 # Custom 404 error page (more useful than the default)
 sphinx-notfound-page==0.7.1