docs(getting_started): Bump NiFi version

Author: NickLarsenNZ

modules/ROOT/pages/getting-started.adoc

@@ -173,7 +173,7 @@ metadata:
   name: simple-nifi
 spec:
   image:
-    productVersion: 1.27.0
+    productVersion: 2.2.0
   clusterConfig:
     listenerClass: external-unstable
     zookeeperConfigMapName: simple-nifi-znode