chore(signal-processing): Remove ZooKeeper operator from stack

There is no need to install the ZooKeeper operator, because no
ZooKeeper cluster is created as part of the demo/stack.

Author: Techassi

demos/demos-v2.yaml

@@ -218,7 +218,6 @@ demos:
       - nifi
       - jupyterhub
       - grafana-dashboards
-      - zookeeper
     manifests:
       - plainYaml: https://raw.githubusercontent.com/stackabletech/demos/main/demos/signal-processing/serviceaccount.yaml
       - plainYaml: https://raw.githubusercontent.com/stackabletech/demos/main/demos/signal-processing/create-timescale-tables.yaml

stacks/stacks-v2.yaml

@@ -617,7 +617,6 @@ stacks:
       - commons
       - listener
       - secret
-      - zookeeper
       - nifi
     labels:
       - timescaledb