build(deps): bump pyyaml from 5.3.1 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.3.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/5.3.1...5.4)

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

requirements.txt

@@ -9,5 +9,5 @@ MarkupSafe==1.1.1
 packaging==20.7
 pycparser==2.20
 pyparsing==2.4.7
-PyYAML==5.3.1
+PyYAML==5.4
 six==1.15.0