Update setup.asciidoc

Update example output after changes in elastic#28 .

Author: Rawk

docs/setup.asciidoc

@@ -40,6 +40,8 @@ logger.debug("Example message!", extra={"http.request.method": "get"})
 ----
 {
     "@timestamp": "2020-03-20T18:11:37.895Z",
+    "log.level": "debug",
+    "message": "Example message!",
     "ecs": {
         "version": "1.6.0"
     },
@@ -49,7 +51,6 @@ logger.debug("Example message!", extra={"http.request.method": "get"})
       }
     },
     "log": {
-        "level": "debug",
         "logger": "app",
         "origin": {
             "file": {
@@ -59,8 +60,7 @@ logger.debug("Example message!", extra={"http.request.method": "get"})
             "function": "func"
         },
         "original": "Example message!"
-    },
-    "message": "Example message!"
+    }
 }
 ----