Update changelog

(cherry picked from commit a562f8f0)

CHANGELOG.rst

@@ -16,6 +16,12 @@ Fixed
 * Set a fixed version for django-sass-processor to avoid a bug with searching ``style.css`` in the wrong storage.
 * Correct the z-index of the navbar to display the main title again on mobile devices.
 
+Removed
+~~~~~~~
+
+* Leftovers from a functionality already dropped in the development process
+  (custom authentication backends and alternative login views).
+
 `2.0rc6`_ - 2021-10-11
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