🩹 Add forgotten disallowed deprecation warning

This deprecation warning was addressed by the following
PR, but we forgot to add it to the list of disallowed
deprecation warnings:

#21614

config/initializers/deprecation_warnings.rb

@@ -20,7 +20,8 @@ module DeprecationWarnings
     /render file: should be given the absolute path to a file/,
     /`ActiveRecord::Result#to_hash` has been renamed to `to_a`/,
     /Class level methods will no longer inherit scoping/,
-    /Controller-level `force_ssl` is deprecated and will be removed from Rails 6\.1/
+    /Controller-level `force_ssl` is deprecated and will be removed from Rails 6\.1/,
+    /NOT conditions will no longer behave as NOR in Rails 6\.1/
   ].freeze
 
   # Regular expressions for deprecation warnings that should raise an exception on detection