build: add support for django42 during GH workflows

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{38}, quality, docs, pii_check
+envlist = py{38}-django{32, 42}, quality, docs, pii_check
 
 
 [doc8]
@@ -38,6 +38,8 @@ norecursedirs = .* docs requirements site-packages
 
 [testenv]
 deps =
+    django32: Django>=3.2,<3.3
+    django42: Django>=4.2,<4.3
     -r{toxinidir}/requirements/test.txt
 commands =
     pytest openedx_events tests