test: remove Django 3.2 environment from tox test environment

Extended support for Django 3.2 ended on 04/01/2024. Dependencies of this library are beginning to require Django >= 4.2, which causes version incompatibilities when running tests in CI in the Django 3.2 environment.

This commit removes the Django 3.2 environment from tox.

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py38-django{32,42}-celery{53}, quality, rst_validation, docs, pii_check
+envlist = py38-django{42}-celery{53}, quality, rst_validation, docs, pii_check
 
 [doc8]
 ignore = D001
@@ -35,7 +35,6 @@ norecursedirs = .* docs requirements site-packages
 
 [testenv]
 deps =
-    django32: Django>=3.2,<4.0
     django42: Django>=4.2,<5.0
     -r{toxinidir}/requirements/test.txt
     celery44: -r{toxinidir}/requirements/celery44.txt