Bump pyyaml from 3.12 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.12 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@3.12...5.4)

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

Author: dependabot[bot]

requirements.txt

@@ -21,7 +21,7 @@ psycopg2==2.8.6
 psycopg2-binary==2.9.1
 python-dotenv==0.19.0
 pytz==2021.1
-PyYAML==3.12
+PyYAML==5.4
 requests==2.19.1
 sqlparse==0.4.1
 tablib==3.0.0