[deploy] Cleanup orphan data from buffer_updates (#10365)

* Cleanup orphan data from backup_data and buffer_updates

* Remove script as the table has been removed

lib/data_update_scripts/20200917135847_nullify_orphan_rows_from_buffer_updates_by_composer_user_id.rb

@@ -0,0 +1,15 @@
+module DataUpdateScripts
+  class NullifyOrphanRowsFromBufferUpdatesByComposerUserId
+    def run
+      # Nullify all BufferUpdates composer_user_id belonging to Users that don't exist anymore
+      ActiveRecord::Base.connection.execute(
+        <<~SQL.squish,
+          UPDATE buffer_updates
+          SET composer_user_id = NULL
+          WHERE composer_user_id IS NOT NULL
+          AND composer_user_id NOT IN (SELECT id FROM users);
+        SQL
+      )
+    end
+  end
+end