Revise tag handling v2 default behavior details

Updated information regarding the default behavior for customers transitioning to tag handling v2.

Author: shirgoldbird

docs/xml-and-html-handling/tag-handling-v2.mdx

@@ -15,9 +15,8 @@ Before switching to `v2`, thoroughly test your system and verify any differences
 Additionally, v2 enforces strict parsing of XML. If invalid XML is submitted, the API will return an error.
 
 <Info>
-  Please note that v2 will become the default on 1 December 2025.
-  To ensure a seamless transition, existing customers will have the option to request v1 for an additional grace period.
-  This will help accommodate integrations that are contingent on particular tag handling behaviours exhibited by v1, for example.
+  Please note that after 1 December 2025, new customers will default to v2 and no longer be able to use v1.
+  Existing customers will continue to default to v1 for the time being, and can opt-in to using v2.
 </Info>
 
 <Info>