Bump pyyaml from 5.1 to 5.4

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.1 to 5.4.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@5.1...5.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-PyYAML==5.1
+PyYAML==5.4
 django==1.11.29
 mistune==0.7.3
 polib==1.0.3

setup.py

@@ -6,7 +6,7 @@
 install_requires = [
     'polib==1.0.3',
     'mistune==0.7.3',
-    'PyYAML==5.1',
+    'PyYAML==5.4',
     'pyparsing==2.2.0',
     'lxml==4.6.2',
     'beautifulsoup4==4.9.3',