[1.6.x] Removed 1.6 release note text regarding password limit length.

This changed was reverted in 5d74853.

Backport of d97bec5 from master

docs/releases/1.6.txt

@@ -810,22 +810,6 @@ as JSON requires string keys, you will likely run into problems if you are
 using non-string keys in ``request.session``. See the
 :ref:`session_serialization` documentation for more details.
 
-4096-byte limit on passwords
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. note::
-    This behavior was also added in the Django 1.5.4 and 1.4.8 security
-    releases.
-
-Historically, Django has imposed no length limit on plaintext
-passwords. This enables a denial-of-service attack through submission
-of bogus but extremely large passwords, tying up server resources
-performing the (expensive, and increasingly expensive with the length
-of the password) calculation of the corresponding hash.
-
-Django now imposes a 4096-byte limit on password length, and will fail
-authentication with any submitted password of greater length.
-
 Miscellaneous
 ~~~~~~~~~~~~~