Change default source_index

documentation/projects/proposals/search_relevancy_sandbox/20230530-implementation_plan_staging_elasticsearch_reindex_dags.md

@@ -131,7 +131,7 @@ Reindex][es_reindex_api] API.
 
 1. `source_index`: (Optional) The existing index on Elasticsearch to use as the
    basis for the new index. If not provided, the index aliased to
-   `<media_type>-full` will be used.
+   `<media_type>-filtered` will be used.
 2. `percentage_of_prod`: A float indicating the proportion of items to take from
    each provider from the total amount existing in production. E.g. `0.25` for a
    quarter of the production documents.