Bump yapf from 0.30.0 to 0.31.0

Bumps [yapf](https://github.com/google/yapf) from 0.30.0 to 0.31.0.
- [Release notes](https://github.com/google/yapf/releases)
- [Changelog](https://github.com/google/yapf/blob/main/CHANGELOG)
- [Commits](google/yapf@v0.30.0...v0.31.0)

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

requirements.txt

@@ -7,4 +7,4 @@ domdf-python-tools>=2.5.0
 isort<=5.6.4,>=5.5.2
 toml>=0.10.2
 typing-extensions>=3.7.4.3
-yapf==0.30.0
+yapf==0.31.0