Documentation Updates for plugins.query.datasources.enabled SQL Setting

This setting allows users to toggle the data source code paths in the
SQL plugin. Ref:

https://github.com/opensearch-project/sql/pull/2811/files

_search-plugins/sql/settings.md

@@ -78,6 +78,7 @@ Setting | Default | Description
 `plugins.sql.cursor.keep_alive` | 1 minute | Configures how long the cursor context is kept open. Cursor contexts are resource-intensive, so we recommend a low value.
 `plugins.query.memory_limit` | 85% | Configures the heap memory usage limit for the circuit breaker of the query engine.
 `plugins.query.size_limit` | 200 | Sets the default size of index that the query engine fetches from OpenSearch.
+`plugins.query.datasources.enabled` | true | Change to `false` to disable the `DataSource` support in the plugin.
 
 ## Spark connector settings