Switched to `JsonSerializer` / `JsonDeserializer`

[demos/kafka/wordcount] / splitter

diff --git a/splitter b/splitter
index 3bc3ef7..836368a 160000 (submodule)
--- a/splitter
+++ b/splitter
@@ -1 +1 @@
-Subproject commit 3bc3ef7ceb76e7643e1e373293cfdc78f870838a
+Subproject commit 836368acb5e435a733df5893e477a406daeafcb3