Revert "Merge pull request rails#46282 from jonathanhefner/active_model-forgetting_assignment-avoid-value_for_database"

This reverts commit 1f039d8, reversing
changes made to be0b5c6.

This revert is temporary while we debug some issues with our app. While
we're pretty sure this is caused by code in our application and a
compbination with `activerecord-typed_store`, the failure mode is easy
to miss because it doesn't raise an exception.

We will un-revert after a bit more investigation. We just want to be
confident that the other cases where this could cause issues are fixed
without being blocked from upgrading for the next month or so.

Author: eileencodes

activemodel/lib/active_model/attribute.rb

@@ -175,19 +175,6 @@ def type_cast(value)
           type.deserialize(value)
         end
 
-        def forgetting_assignment
-          # If this attribute was not persisted (with a `value_for_database`
-          # that might differ from `value_before_type_cast`) and `value` has not
-          # changed in place, we can simply dup this attribute to avoid
-          # deserialize / cast / serialize calls from computing the new
-          # attribute's `value_before_type_cast`.
-          if !defined?(@value_for_database) && !changed_in_place?
-            dup
-          else
-            super
-          end
-        end
-
         private
           def _original_value_for_database
             value_before_type_cast