doc: clarify that APIs are no longer experimental

Change "no longer considered experimental" to "no longer experimental".
It's more clear and direct.

PR-URL: https://github.com/nodejs/node/pull/34113


Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>