Update the upgrade guide

docs/upgrade-guides/core/3-20-to-3-21.mdx

@@ -11,7 +11,7 @@ Otherwise, you will need to downtime your solution to ensure correct data migrat
 ## Authentication required for changing `Order` and `OrderLine` metadata
 
 The [updateMetadata](/api-reference/miscellaneous/mutations/update-metadata.mdx) mutation for `Order` and `OrderLine` now requires the `MANAGE_ORDERS` permission.
-After an order is created, customers cannot edit its metadata. Merchants, however, can modify this data using an app built with the appropriate permission.
+Once an order is created, customers cannot edit its metadata. However, merchants and apps with the necessary permissions can modify this data.
 Fetching metadata remains unchanged.
 
 ## Deprecated `manager.perform_mutation` method