Change 'STAC Order specification' to 'STAC Order extension' for consistency.

Author: janjezersek

extensions/commercial-data/README.md

@@ -23,7 +23,7 @@ When the order is completed, the data is ingested in a collection and its ID is
 
 A backend should add general information about a commercial data collection to the `/collections` and `/collections/{collection_id}` endpoints, the same as with freely available collections. Only the metadata about the entire dataset needs to be provided, not about the specific data products that a user has already purchased. 
 
-Commercial data collections are distinguished from freely available collections by including `"order:status": "orderable"` as specified in the [STAC Order specification](https://github.com/stac-extensions/order/tree/v1.0.0).
+Commercial data collections are distinguished from freely available collections by including `"order:status": "orderable"` as specified in the [STAC Order extension](https://github.com/stac-extensions/order/tree/v1.0.0).
 
 Commercial data collections can include an `order_parameters` field if ordering supports additional parameters that specify how the products should be delivered.