Bump flake8-isort in /{{cookiecutter.app_name}}/requirements

Bumps [flake8-isort](https://github.com/gforcada/flake8-isort) from 2.7.0 to 2.8.0.
- [Release notes](https://github.com/gforcada/flake8-isort/releases)
- [Changelog](https://github.com/gforcada/flake8-isort/blob/master/CHANGES.rst)
- [Commits](https://github.com/gforcada/flake8-isort/compare/2.7.0...2.8.0)

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

{{cookiecutter.app_name}}/requirements/dev.txt

@@ -13,6 +13,6 @@ flake8==3.7.9
 flake8-blind-except==0.1.1
 flake8-debugger==3.2.1
 flake8-docstrings==1.5.0
-flake8-isort==2.7.0
+flake8-isort==2.8.0
 isort==4.3.21
 pep8-naming==0.9.1