Bump pyyaml from 3.11 to 5.4 in /requirements

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.11 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@3.11...5.4)

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

Author: dependabot[bot]

requirements/runtime.txt

@@ -1,4 +1,4 @@
 docopt==0.6.2      # Create CLI from a docstring
 semver==2.0.2      # To match semver-compliant version numbers
-PyYAML==3.11       # To parse ep.yml files
+PyYAML==5.4       # To parse ep.yml files
 wheel==0.24.0      # To package in wheel format