Bump pyyaml from 5.1.2 to 5.4 (#402)

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](https://github.com/yaml/pyyaml/compare/5.1.2...5.4)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements.txt

@@ -181,7 +181,7 @@ pyobjc-framework-Vision==6.2.2
 pyobjc-framework-WebKit==6.2.2
 pyparsing==2.4.1.1
 python-dateutil==2.8.1
-PyYAML==5.1.2
+PyYAML==5.4
 pyzmq==18.1.1
 readme-renderer==25.0
 regex==2020.2.20