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](yaml/pyyaml@5.3.1...5.4)

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

requirements.txt

@@ -3,7 +3,7 @@ botocore==1.17.20
 docutils==0.15.2
 jmespath==0.10.0
 python-dateutil==2.8.1
-PyYAML==5.3.1
+PyYAML==5.4
 s3transfer==0.3.3
 six==1.15.0
 urllib3==1.25.9