docs: update url deprecation copy [skip ci]

Co-authored-by: Allen Dean <[email protected]>

Author: mediumTaj

README.md

@@ -27,7 +27,7 @@ The .NET Standard SDK uses [Watson][wdc] services, a collection of REST APIs tha
 
 ## ANNOUNCEMENTS!
 ### Updating endpoint URLs from watsonplatform.net
-Watson API endpoint URLs at watsonplatform.net are changing and will not work after they are retired. Update your calls to use the newer endpoint URLs. Please see https://cloud.ibm.com/docs/watson?topic=watson-endpoint-change for details.
+Watson API endpoint URLs at watsonplatform.net are changing and will not work after 26 May 2021. Update your calls to use the newer endpoint URLs. For more information, see https://cloud.ibm.com/docs/watson?topic=watson-endpoint-change.
 
 ### Personality Insights deprecation
 IBM Watson™ Personality Insights is discontinued. For a period of one year from 1 December 2020, you will still be able to use Watson Personality Insights. However, as of 1 December 2021, the offering will no longer be available.