fix: downgrade knative-serving

Author: Jehoszafat Zimnowoda

values/knative/knative-serving-raw.gotmpl

@@ -6,7 +6,7 @@ resources:
       name: knative-serving
       namespace: knative-serving
     spec:
-      version: 0.18.0
+      version: 0.17.0
       config:
         defaults:
           revision-timeout-seconds: "300"  # 5 minutes