Bump pyyaml from 4.2b4 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 4.2b4 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/commits/5.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 jsonschema
 openapi-schema-validator
-PyYAML==4.2b4
+PyYAML==5.4
 six==1.12.0
 requests