build: suppress Django deprecation warnings (#29528)

Suppress them both in tests (via setup.py and pytest.ini)
and in management command & application runs
(via logsettings.py).

Developers aren't looking at these warnings; they'll be dealt with in a
formal process for upgrading Django.  Suppress them for now so that
important information isn't lost in the noise.

cms/pytest.ini

@@ -8,6 +8,8 @@ filterwarnings =
     default
     ignore:No request passed to the backend, unable to rate-limit:UserWarning
     ignore::xblock.exceptions.FieldDataDeprecationWarning
+    ignore::django.utils.deprecation.RemovedInDjango40Warning
+    ignore::django.utils.deprecation.RemovedInDjango41Warning
 norecursedirs = envs
 python_classes =
 python_files = test.py tests.py test_*.py *_tests.py