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] <support@github.com>

requirements.txt

@@ -39,7 +39,7 @@ pypiwin32==223
 pyreadline==2.1
 python-dateutil==2.7.5
 pywin32==224
-PyYAML==4.2b4
+PyYAML==5.4
 requests==2.21.0
 requests-oauthlib==1.2.0
 six==1.12.0