fix(stacks/signal-processing): Update image version used in demo

Author: NickLarsenNZ

stacks/signal-processing/jupyterhub.yaml

@@ -41,7 +41,7 @@ options:
       # TODO (@NickLarsenNZ): Use a versioned image with stackable0.0.0-dev or stackableXX.X.X so that
       # the demo is reproducable for the release and it will be automatically replaced for the release branch.
       name: oci.stackable.tech/demos/jupyter-pyspark-with-alibi-detect
-      tag: python-3.9
+      tag: python-3.12
     cloudMetadata:
       # Disable, otherwise we get Back-off restarting failed container block-cloud-metadata in pod:
       # block-cloud-metadata iptables v1.8.9 (legacy): can't initialize iptables table `filter': Table does not exist (do you need to insmod?)