Change legacy template deprecation message (#72147)

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestPutIndexTemplateAction.java

@@ -29,8 +29,7 @@ import static org.elasticsearch.rest.RestRequest.Method.PUT;
 public class RestPutIndexTemplateAction extends BaseRestHandler {
 
     private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(RestPutIndexTemplateAction.class);
-    public static final String DEPRECATION_WARNING = "Legacy index templates are deprecated and will be removed completely in a " +
-        "future version. Please use composable templates instead.";
+    public static final String DEPRECATION_WARNING = "Legacy index templates are deprecated in favor of composable templates.";
     private static final RestApiVersion DEPRECATION_VERSION = RestApiVersion.V_8;
     public static final String TYPES_DEPRECATION_MESSAGE = "[types removal]" +
         " Specifying include_type_name in put index template requests is deprecated."+