doc: remove experimental status for JSON documentation

The JSON documentation is relied up on by some consumers. It has been in
Experimental status for a long time. Promote it to Stable.

Reword the JSON documentation overview for brevity and clarity.

PR-URL: #27842
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/documentation.md

@@ -54,12 +54,8 @@ attaching a listener to the [`'warning'`][] event.
 added: v0.6.12
 -->
 
-> Stability: 1 - Experimental
-
-Every `.html` document has a corresponding `.json` document presenting
-the same information in a structured manner. This feature is
-experimental, and added for the benefit of IDEs and other utilities that
-wish to do programmatic things with the documentation.
+Every `.html` document has a corresponding `.json` document. This is for IDEs
+and other utilities that consume the documentation.
 
 ## Syscalls and man pages