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] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -89,7 +89,7 @@ pytest-cov==2.10.1
 python-dateutil==2.8.1
 python-dotenv==0.15.0
 PyWavelets==1.1.1
-PyYAML==5.3.1
+PyYAML==5.4
 pyzmq==22.0.2
 qtconsole==5.0.2
 QtPy==1.9.0