Revert "Improve cookie based session backend docs." refs #20418

This reverts commit d9c01da1f8ba3d4e0947fd1d619c8f4a9b013360.

This is poor advice as it breaks the test client login (refs #22934).
We can add a note like this back after refs #22986 is resolved.

docs/topics/http/sessions.txt

@@ -119,13 +119,6 @@ To use cookies-based sessions, set the :setting:`SESSION_ENGINE` setting to
 stored using Django's tools for :doc:`cryptographic signing </topics/signing>`
 and the :setting:`SECRET_KEY` setting.
 
-.. note::
-
-    When using cookies-based sessions :mod:`django.contrib.sessions` can be
-    removed from :setting:`INSTALLED_APPS` setting because data is loaded
-    from the key itself and not from the database, so there is no need for the
-    creation and usage of ``django.contrib.sessions.models.Session`` table.
-
 .. note::
 
     It's recommended to leave the :setting:`SESSION_COOKIE_HTTPONLY` setting