Switched to `JsonSerializer` / `JsonDeserializer`

[demos/kafka/wordcount] / query

diff --git a/query b/query
index 251cf79..f929a47 160000 (submodule)
--- a/query
+++ b/query
@@ -1 +1 @@
-Subproject commit 251cf79927d4c1c941467c8fee0349c1a7eb4b93
+Subproject commit f929a47a66a2c14a291133aaa624ad9c5696bd53