fix: Don't let istio to instrument the webhook

Istio and the api-sever does not play pretty well together, like pizza
and pineapple:

* istio/istio#8696
* istio/istio#12187

Chart is open enough for the users to set the podAnnotation with the
api-server instead of not deploying the sidecar in the webhook, but by
default we offer an option that works on most possible scenarios.

charts/admission-controller/values.yaml

@@ -53,6 +53,7 @@ webhook:
     prometheus.io/path: "/metrics"
     prometheus.io/port: "5000"
     prometheus.io/scheme: "https"
+    sidecar.istio.io/inject: "false"
 
   podSecurityContext: {}