Bump pyyaml from 5.3.1 to 5.4 in /requirements

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](https://github.com/yaml/pyyaml/compare/5.3.1...5.4)

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

requirements/prod.txt

@@ -7,7 +7,7 @@ idna==2.10
 langdetect==1.0.8
 lxml==4.5.1
 PySocks==1.7.1
-PyYAML==5.3.1
+PyYAML==5.4
 requests==2.24.0
 schedule==0.6.0
 selenium==3.141.0