v8: mark serdes API as stable

This has been around for a long time, and the underlying V8 API has
become stable as well a while ago.

PR-URL: #30234
Reviewed-By: Gireesh Punathil <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Gus Caplan <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Jiawen Geng <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: James M Snell <[email protected]>

doc/api/v8.md

@@ -266,8 +266,6 @@ if (isMainThread) {
 
 ## Serialization API
 
-> Stability: 1 - Experimental
-
 The serialization API provides means of serializing JavaScript values in a way
 that is compatible with the [HTML structured clone algorithm][].
 The format is backward-compatible (i.e. safe to store to disk).