doc: show output of example in http

User can check output of example easily.

PR-URL: #45915
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/http.md

@@ -3664,9 +3664,9 @@ const { validateHeaderName } = require('node:http');
 try {
   validateHeaderName('');
 } catch (err) {
-  err instanceof TypeError; // --> true
-  err.code; // --> 'ERR_INVALID_HTTP_TOKEN'
-  err.message; // --> 'Header name must be a valid HTTP token [""]'
+  console.error(err instanceof TypeError); // --> true
+  console.error(err.code); // --> 'ERR_INVALID_HTTP_TOKEN'
+  console.error(err.message); // --> 'Header name must be a valid HTTP token [""]'
 }
 ```
 
@@ -3698,17 +3698,17 @@ const { validateHeaderValue } = require('node:http');
 try {
   validateHeaderValue('x-my-header', undefined);
 } catch (err) {
-  err instanceof TypeError; // --> true
-  err.code === 'ERR_HTTP_INVALID_HEADER_VALUE'; // --> true
-  err.message; // --> 'Invalid value "undefined" for header "x-my-header"'
+  console.error(err instanceof TypeError); // --> true
+  console.error(err.code === 'ERR_HTTP_INVALID_HEADER_VALUE'); // --> true
+  console.error(err.message); // --> 'Invalid value "undefined" for header "x-my-header"'
 }
 
 try {
   validateHeaderValue('x-my-header', 'oʊmɪɡə');
 } catch (err) {
-  err instanceof TypeError; // --> true
-  err.code === 'ERR_INVALID_CHAR'; // --> true
-  err.message; // --> 'Invalid character in header content ["x-my-header"]'
+  console.error(err instanceof TypeError); // --> true
+  console.error(err.code === 'ERR_INVALID_CHAR'); // --> true
+  console.error(err.message); // --> 'Invalid character in header content ["x-my-header"]'
 }
 ```