stronger wording around upgrade policy

Author: themar-msft

articles/chaos-studio/troubleshooting.md

@@ -63,7 +63,7 @@ Installing the Chaos agent on Virtual Machine Scale Sets may fail with without s
 1. From the left pane menu, choose **Upgrade policy**.
 1. Check the **Upgrade mode** to see if it's set to **Manual - Existing instances must be manually upgraded**.
 
-If the Upgrade policy is set to **Manual**, you can manually upgrade your VMSS instances so that you can install the Chaos agent.
+If the Upgrade policy is set to **Manual**, you must upgrade your VMSS instances so that Chaos agent installation completes.
 
 #### Upgrade instances from Azure portal