Update how-to-create-user-defined-route-instance.md

Fix CLI command issue

Author: ShichaoQiu

articles/spring-apps/how-to-create-user-defined-route-instance.md

@@ -214,7 +214,8 @@ az network firewall network-rule create \
     --protocols 'TCP' \
     --source-addresses '*' \
     --destination-addresses "AzureCloud" \
-    --destination-ports 443 445
+    --destination-ports 443 445 \
+    --action allow --priority 100
 
 # Add firewall application rules.