Mark the /_create_from/{source}/{dest} API as public on Serverless

Related to elastic/elasticsearch#134953

Author: dakrone

specification/indices/create_from/MigrateCreateFromRequest.ts

@@ -28,7 +28,7 @@ import { IndexSettings } from '@indices/_types/IndexSettings'
  * Copy the mappings and settings from the source index to a destination index while allowing request settings and mappings to override the source values.
  * @rest_spec_name indices.create_from
  * @availability stack since=8.18.0 stability=experimental
- * @availability serverless stability=experimental visibility=private
+ * @availability serverless stability=experimental visibility=public
  * @doc_id migration-api-create-from
  * @doc_tag migration
  */