fix(shared): Reduce scope for database network policy

This patch reduces the network acess from the database mangeement
namespace to postgres-operator only. (Technically speaking there isn't
anything else running in that namespace, but it helps to keep things
tight in case of future expansions.)

shared/networkpolicies/allow-from-database.yaml

@@ -10,6 +10,9 @@ spec:
     - namespaceSelector:
         matchLabels:
           database.shivering-isles.com/network-access-required: "true"
+      podSelector:
+        matchLabels:
+          app.kubernetes.io/name: postgres-operator
     ports:
     - port: 8008
       protocol: TCP