chore(deps): update dependency pyyaml to v3.13

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
PyYaml (source)	==3.12 -> ==3.13

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Release Notes

yaml/pyyaml

### [`v3.13`](https://togithub.com/yaml/pyyaml/blob/master/CHANGES#​313-2018-07-05) [Compare Source](https://togithub.com/yaml/pyyaml/compare/3.12...3.13) - Resolved issues around PyYAML working in Python 3.7.

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