Revert "FIX: Post uploads setting access_control_post_id unnecessarily (#26627)" (#26643)

This reverts commit cdc8e9de1b.

It's made things worse internally and on meta.

app/models/upload_reference.rb

@@ -6,10 +6,6 @@ class UploadReference < ActiveRecord::Base
 
   delegate :to_markdown, to: :upload
 
-  def target?(target_to_check)
-    self.target_id == target_to_check.id && self.target_type == target_to_check.class.to_s
-  end
-
   def self.ensure_exist!(upload_ids: [], target: nil, target_type: nil, target_id: nil)
     if !target && !(target_type && target_id)
       raise "target OR target_type and target_id are required"