build(deps): bump pyyaml from 5.3.1 to 5.4.1 in /bot (#742)

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.3.1 to 5.4.1.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@5.3.1...5.4.1)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

bot/requirements.txt

@@ -3,7 +3,7 @@ google-cloud-storage==1.35.0
 libmozdata==0.1.68
 pytoml==0.1.21
 pytz==2020.5
-pyyaml==5.3.1
+pyyaml==5.4.1
 tenacity==6.3.1
 tqdm==4.56.0
 zstandard==0.15.1