Make frontend deployment auto scale (#2736)

Now that we have effective global sessions thanks to #2734, there is no
longer a need to keep the number of pods on the EPP service static.

We are also not vulnerable to random pod restarts. K8s never guarantees
perpetual pod lifetime anyway, and not having to be at its mercy is
certainly a relief.

jetty/kubernetes/nomulus-frontend.yaml

@@ -82,8 +82,8 @@ spec:
     apiVersion: apps/v1
     kind: Deployment
     name: frontend
-  minReplicas: 15
-  maxReplicas: 15
+  minReplicas: 5
+  maxReplicas: 20
   metrics:
     - type: Resource
       resource: