doc: fix actual result of example is different in stream

Error message of JSON.parse may be changed with current node version.
For reference, actual result is same with previous node
version(v16.18.1).

PR-URL: nodejs#45619
Reviewed-By: Kohei Ueno <kohei.ueno119@gmail.com>
Reviewed-By: Daeyeon Jeong <daeyeon.dev@gmail.com>

doc/api/stream.md

@@ -172,7 +172,7 @@ server.listen(1337);
 // $ curl localhost:1337 -d "\"foo\""
 // string
 // $ curl localhost:1337 -d "not json"
-// error: Unexpected token o in JSON at position 1
+// error: Unexpected token 'o', "not json" is not valid JSON
 ```
 
 [`Writable`][] streams (such as `res` in the example) expose methods such as