Updating serverless docs (elastic#172)

* fixing exists API link

* fixing images on index management page

Author: georgewallace

serverless/images/index-management-index-templates.png

@@ -18,7 +18,7 @@ Elasticsearch returns an `index_not_found_exception` when the data stream, index
 or alias you try to query does not exist. This can happen when you misspell the
 name or when the data has been indexed to a different data stream or index.
 
-Use the https://www.elastic.co/docs/api/doc/elasticsearch-serverless/operation/operation-indices-exists-index-template[**Exists API**] to check whether
+Use the https://www.elastic.co/docs/api/doc/elasticsearch-serverless/operation/operation-indices-exists[**Exists API**] to check whether
 a data stream, index, or alias exists:
 
 [source,js]

serverless/images/index-management-indices.png

@@ -97,7 +97,7 @@ To view information about the stream's backing indices, click the number in the
 * To view more information about a data stream, such as its generation or its
 current index lifecycle policy, click the stream's name. From this view, you can navigate to **Discover** to
 further explore data within the data stream.
-* preview:[] To edit the data retention value, open the **Manage** menu, and then click **Edit data retention**.
+* preview:[] To modify the data retention value, select an index, open the **Manage**  menu, and click **Edit data retention**.
 
 ////
 /*