chore(deps): bump pyyaml from 5.3.1 to 5.4 in /pipelines

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.3.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@5.3.1...5.4)

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

Author: dependabot[bot]

pipelines/requirements.txt

@@ -63,7 +63,7 @@ pyOpenSSL==19.1.0
 pyparsing==2.4.7
 python-dateutil==2.8.1
 pytz==2020.1
-PyYAML==5.3.1
+PyYAML==5.4
 requests==2.23.0
 requests-oauthlib==1.3.0
 retrying==1.3.3