Bump pyyaml from 3.13 to 5.1

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.13 to 5.1.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/3.13...5.1)

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/requirements.txt b/requirements.txt
index 30efd89..d546330 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 paramiko>=1.16.0,<2.0.1
-PyYAML==3.13
+PyYAML==5.1
 six>=1.9.0
 cookiecutter
 jinja2==2.8.1