Make the 'get templates' types deprecation message consistent. (elastic#38549)

Author: jtibshirani

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

@@ -51,8 +51,8 @@ public class RestGetIndexTemplateAction extends BaseRestHandler {
         Collections.singleton(INCLUDE_TYPE_NAME_PARAMETER), Settings.FORMAT_PARAMS));
     private static final DeprecationLogger deprecationLogger = new DeprecationLogger(
             LogManager.getLogger(RestGetIndexTemplateAction.class));
-    public static final String TYPES_DEPRECATION_MESSAGE = "[types removal]" +
-            " Specifying include_type_name in get index template requests is deprecated.";
+    public static final String TYPES_DEPRECATION_MESSAGE = "[types removal] Using include_type_name in get " +
+        "index template requests is deprecated. The parameter will be removed in the next major version.";
 
     public RestGetIndexTemplateAction(final Settings settings, final RestController controller) {
         super(settings);