Bump isort from 5.1.1 to 5.1.4 in /src/requirements (#590)

Bumps [isort](https://github.com/timothycrosley/isort) from 5.1.1 to 5.1.4.
- [Release notes](https://github.com/timothycrosley/isort/releases)
- [Changelog](https://github.com/timothycrosley/isort/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/timothycrosley/isort/compare/5.1.1...5.1.4)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

src/requirements/dev.txt

@@ -6,6 +6,6 @@ coverage==5.2
 codecov==2.1.8
 black==19.10b0
 pre-commit==2.6.0
-isort==5.1.1
+isort==5.1.4
 hypothesis==5.20.3
 flake8==3.8.3