doc: remove Legacy status from querystring

Closes: #44911
PR-URL: #44912
Fixes: #44911
Reviewed-By: Erick Wendel <erick.workspace@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

Author: Trott

doc/api/querystring.md

@@ -2,7 +2,7 @@
 
 <!--introduced_in=v0.1.25-->
 
-> Stability: 3 - Legacy
+> Stability: 2 - Stable
 
 <!--name=querystring-->
 
@@ -15,8 +15,9 @@ query strings. It can be accessed using:
 const querystring = require('node:querystring');
 ```
 
-The `querystring` API is considered Legacy. While it is still maintained,
-new code should use the {URLSearchParams} API instead.
+`querystring` is more performant than {URLSearchParams} but is not a
+standardized API. Use {URLSearchParams} when performance is not critical or
+when compatibility with browser code is desirable.
 
 ## `querystring.decode()`