Update migration-isv-guidance.md (SharePoint#4470)

Content update:  Removed line referring to future release.

Author: JoanneHendrickson

docs/apis/migration-isv-guidance.md

@@ -78,7 +78,7 @@ A new migration API, Asynchronous Metadata Read API (Export API) is currently be
 
 - [Asynchronous Metadata Read (Export API)](https://docs.microsoft.com/en-us/sharepoint/dev/apis/export-amr-api)
 
-The *AsynchronousMetadataRead* helps the ISVs export content from SharePoint and OneDrive.  Once the new API becomes available, we recommend that you transition to the new API to avoid throttling.
+The *AsynchronousMetadataRead* helps the ISVs export content from SharePoint and OneDrive.
 
 ## Switch to the Microsoft Graph API 
 If a feature is not supported by the migration API, we recommend that you use the Graph API.  If the Graph API does not support the needed migration feature, then use CSOM. However, using CSOM increases the likelihood of being throttled.