Bump pyyaml from 5.1.2 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.1.2 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@5.1.2...5.4)

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

requirements.txt

@@ -43,7 +43,7 @@ python-dateutil==2.8.1
 python-dotenv==0.10.3
 python-editor==1.0.4
 pytz==2019.3
-PyYAML==5.1.2
+PyYAML==5.4
 redis==3.3.11
 selenium==3.141.0
 six==1.12.0