Bump isort from 5.6.3 to 5.6.4

Bumps [isort](https://github.com/pycqa/isort) from 5.6.3 to 5.6.4.
- [Release notes](https://github.com/pycqa/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/pycqa/isort/compare/5.6.3...5.6.4)

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

requirements-dev.txt

@@ -13,7 +13,7 @@ pytest-asyncio==0.14.0
 pytest-cov==2.10.1
 pytest-mock==3.3.1
 pytest-random-order==1.0.4
-isort==5.6.3
+isort==5.6.4
 
 # Convert jupyter notebooks to markdown documents
 nbconvert==6.0.7