Update ubuntu-pro-in-place-upgrade.md

Making sure we have the disclaimer about limitations and images that can't be upgraded to PRO for this process.

Making sure we convert from NOTE to IMPORTANT about the process being irreversible.

Author: mabicca

articles/virtual-machines/workloads/canonical/ubuntu-pro-in-place-upgrade.md

@@ -23,6 +23,10 @@ their servers from Ubuntu 18.04 LTS now that it's reached End of Life (EOL).
 > software updates, or security patches for this version. Customers wishing to continue using Ubuntu
 > 18.04 LTS need to upgrade to Ubuntu Pro for continued supportability.
 
+## Limitations
+- Only Ubuntu images **published by Canonical** can be converted to "UBUNTU_PRO"
+- Images published by other vendors or custom images are not supported
+
 ## What's Ubuntu Pro?
 
 Ubuntu Pro is a cross-cloud OS, optimized for Azure, and security maintained for 10 years. The
@@ -51,9 +55,11 @@ packages.
 - Portability: Ubuntu is available in all regions with content mirrors to reduce the need to go across regions or out to the Internet for updates
 - Consistent experience across platforms: from edge to multicloud, Ubuntu provides the same experience regardless of the platform. It ensures consistency of your CI/CD pipelines and management mechanisms.
 
-> [!NOTE]
+> [!IMPORTANT]
 > This document provides instructions to upgrade Ubuntu Server (16.04 or higher) to
-> Ubuntu Pro. Converting to Ubuntu Pro is an irreversible process.
+> Ubuntu Pro.
+> 
+> Converting to Ubuntu Pro is an **irreversible** process.
 
 ## Convert to Ubuntu Pro using the Azure CLI