Bump pyyaml from 5.1.1 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.1.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@5.1.1...5.4)

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

Author: dependabot[bot]