Also update isort for tox

--recursive is no longer needed, see https://timothycrosley.github.io/isort/docs/upgrade_guides/5.0.0/

Author: davidweterings

Makefile

@@ -20,7 +20,7 @@ runserver:
 	python -mcommercetools.testing.server
 
 format:
-	isort --recursive src tests codegen
+	isort src tests codegen
 	black src/ tests/ codegen/
 
 release:

tox.ini

@@ -25,8 +25,8 @@ commands =
 basepython = python3.7
 deps =
     black==18.9b0
-    isort[toml]==4.3.21
+    isort[toml]==5.2.2
 skip_install = true
 commands =
-    isort --recursive --check-only src tests
+    isort --check-only src tests
     black --check src/ tests/