Switched to `JsonSerializer` / `JsonDeserializer`

[demos/kafka/wordcount] / fortune

diff --git a/fortune b/fortune
index dde18ef..8c69a7c 160000 (submodule)
--- a/fortune
+++ b/fortune
@@ -1 +1 @@
-Subproject commit dde18ef24d54bb988ad458ad6e12ed99fbc53061
+Subproject commit 8c69a7caad51f067f129a751966d0f4638fa228c