Refined output JSON for service `popular`

[demos/kafka/wordcount] / popular

diff --git a/popular b/popular
index feb9d86..8af553a 160000 (submodule)
--- a/popular
+++ b/popular
@@ -1 +1 @@
-Subproject commit feb9d86212983d93d3546f5a4d9b15f14cd57314
+Subproject commit 8af553a2b1cae0b7f5c9d9c63023b47af89bd5ab