chore(stack/observability): Disable Loki Canery

It only generates noise which is not needed for the demo.

Author: NickLarsenNZ

stacks/observability/grafana-loki.yaml

@@ -77,5 +77,7 @@ options:
         installOperator: false
   test:
     enabled: false
+  lokiCanary:
+    enabled: false
   gateway:
     enabled: false