Bump pyyaml from 5.3.1 to 5.4

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]

requirements.txt

@@ -3,5 +3,5 @@ discord==1.0.1
 emoji==0.6.0
 google_api_python_client==1.10.0
 praw==7.1.0
-PyYAML==5.3.1
+PyYAML==5.4
 youtube_dl==2020.7.28