Bump pyyaml from 5.3.1 to 5.4 (#35)

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] <support@github.com>

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

requirements.txt

@@ -3,7 +3,7 @@ torchtext==0.7.0
 sacrebleu==1.4.14
 sacremoses==0.0.43
 spacy==2.3.2
-PyYAML==5.3.1
+PyYAML==5.4
 tqdm==4.50.0
 Unidecode==1.1.1
 tokenizers==0.8.1rc2