correct name of ContentBlockManager engine in migration

although it is not good practice to edit past
migrations, we think this is safe to do as it
doesn't change the actual migration, and not
changing it could cause problems/confusion in the
future.

db/migrate/20240725144121_add_latest_edition_info_to_content_block_documents.rb

@@ -1,6 +1,6 @@
 class AddLatestEditionInfoToContentBlockDocuments < ActiveRecord::Migration[7.1]
   def up
-    ContentObjectStore::ContentBlock::Document.find_each do |document|
+    ContentBlockManager::ContentBlock::Document.find_each do |document|
       if document.latest_edition_id.nil? || document.live_edition_id.nil?
         document.update!(
           latest_edition_id: document.content_block_editions.last.id,
@@ -11,7 +11,7 @@ def up
   end
 
   def down
-    ContentObjectStore::ContentBlock::Document.update_all(
+    ContentBlockManager::ContentBlock::Document.update_all(
       latest_edition_id: nil,
       live_edition_id: nil,
     )