Updated PubSub Chat sample to create proper hub

I've changed the az cli command to create the proper hub aligned to the sample code otherwise the ngrock will never being fired!

Author: algorni

articles/azure-web-pubsub/tutorial-build-chat.md

@@ -607,7 +607,7 @@ Use the Azure CLI [az webpubsub hub create](/cli/azure/webpubsub/hub#az_webpubsu
   > Replace <domain-name> with the name ngrok printed.
 
 ```azurecli-interactive
-az webpubsub hub create -n "<your-unique-resource-name>" -g "myResourceGroup" --hub-name "chat" --event-handler url-template="https://<domain-name>.ngrok.io/eventHandler" user-event-pattern="*" system-event="connected"
+az webpubsub hub create -n "<your-unique-resource-name>" -g "myResourceGroup" --hub-name "SampleChatHub" --event-handler url-template="https://<domain-name>.ngrok.io/eventHandler" user-event-pattern="*" system-event="connected"
 ```
 
 After the update is completed, open the home page http://localhost:8080/index.html, input your user name, you’ll see the connected message printed in the server console.