Revert tox.ini Django 4.0.1 constraint

* As of Dec 19, 2021, Django 4.0.1 has not released changes to fix a regression.It is a user-end regression that does not affect usability, but it does affect user's belief that they need to create a migration. In @Andrew-Chen-Wang's past experience, that has led to production errors and an emergency migration of one of his past packages...

Author: Andrew-Chen-Wang

tox.ini

@@ -36,7 +36,7 @@ setenv =
 deps =
     dj22: Django>=2.2,<3
     dj32: Django>=3.2,<3.3
-    dj40: Django>=4.0.1,<4.1
+    dj40: Django>=4.0.0,<4.1
     djmain: https://github.com/django/django/archive/main.tar.gz
     djangorestframework
     oauthlib>=3.1.0