Let through reflections delegate deprecated? to their delegate

I am trying to find the right spot for HABTMs and deprecation.

The current logic checking parent_reflection by hand seems suspiciously ad-hoc
for me but, at the same time, I was trying to keep the option flag strictly
where the user set it.

However, through reflections act as their delegate for the most part:

    delegate_methods = AssociationReflection.public_instance_methods -
      public_instance_methods

    delegate(*delegate_methods, to: :delegate_reflection)

If I sacrifice the rule above just a bit, the internal has_many of HABTMs could
carry the option if present, and the resulting code looks simpler and maybe more
aligned with the current design.

Author: fxn

activerecord/lib/active_record/associations.rb

@@ -2035,7 +2035,7 @@ def destroy_associations
           hm_options[:through] = middle_reflection.name
           hm_options[:source] = join_model.right_reflection.name
 
-          [:before_add, :after_add, :before_remove, :after_remove, :autosave, :validate, :join_table, :class_name, :extend, :strict_loading].each do |k|
+          [:before_add, :after_add, :before_remove, :after_remove, :autosave, :validate, :join_table, :class_name, :extend, :strict_loading, :deprecated].each do |k|
             hm_options[k] = options[k] if options.key?(k)
           end
 

activerecord/lib/active_record/reflection.rb

@@ -1217,19 +1217,6 @@ def add_as_through(seed)
         collect_join_reflections(seed + [self])
       end
 
-      def deprecated?
-        unless defined?(@deprecated)
-          @deprecated =
-            if parent_reflection.is_a?(HasAndBelongsToManyReflection)
-              parent_reflection.deprecated?
-            else
-              delegate_reflection.deprecated?
-            end
-        end
-
-        @deprecated
-      end
-
       def deprecated_nested_reflections
         @deprecated_nested_reflections ||= collect_deprecated_nested_reflections
       end