apps/ninja: temporarily downgrade for restoration

apps/ninja/invoiceninja/invoiceninja-values-configmap.yaml

@@ -8,7 +8,7 @@ data:
     # https://github.com/invoiceninja/dockerfiles/blob/master/charts/invoiceninja/values.yaml
     image:
       # https://hub.docker.com/r/invoiceninja/invoiceninja/tags
-      tag: 5.9
+      tag: 5.8
       pullPolicy: Always
     ingress:
       enabled: true