tox: test django 4.0 final

Author: bluetech

tox.ini

@@ -12,7 +12,7 @@ envlist =
 extras = testing
 deps =
     djmain: https://github.com/django/django/archive/main.tar.gz
-    dj40: Django>=4.0a1,<4.1
+    dj40: Django>=4.0,<4.1
     dj32: Django>=3.2,<4.0
     dj31: Django>=3.1,<3.2
     dj22: Django>=2.2,<2.3