Bump pyyaml from 3.13 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.13 to 5.4.
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@3.13...5.4)

---
updated-dependencies:
- dependency-name: pyyaml
  dependency-type: direct:production
...

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

requirements.txt

@@ -28,7 +28,7 @@ pytest-pep8==1.0.6
 pytest-spec==1.1.0
 pytest-sugar==0.9.2
 pytest-watch==4.2.0
-PyYAML==3.13
+PyYAML==5.4
 six==1.12.0
 termcolor==1.1.0
 watchdog==0.9.0