fix(ci): Django main branch requires 3.12+

Author: pennersr

tox.ini

@@ -2,7 +2,7 @@
 envlist =
     prj{regular,headless_only}-py{38,39,310,311,312}-django{42}
     prj{regular,headless_only}-py{310,311,312}-django{50,51}
-    prj{regular,headless_only}-py{310,311,312}-djangomain
+    prj{regular,headless_only}-py{312}-djangomain
     prj{login_required_mw}-py{312}-django{51}
     docs
     isort