[DOCS] Nest clone snapshot API page with other APIs

#61839 introduced the [Clone snapshot API](https://www.elastic.co/guide/en/elasticsearch/reference/master/clone-snapshot-api.html). That page should be moved under the [Snapshot and restore REST APIs](https://www.elastic.co/guide/en/elasticsearch/reference/master/snapshot-restore-apis.html) section to nest with the other snapshot and restore APIs.