doc: align maxHeaderSize default with current value

PR-URL: #41183
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ricky Zhou <0x19951125@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/http.md

@@ -2996,7 +2996,7 @@ added:
 * {number}
 
 Read-only property specifying the maximum allowed size of HTTP headers in bytes.
-Defaults to 8 KB. Configurable using the [`--max-http-header-size`][] CLI
+Defaults to 16 KB. Configurable using the [`--max-http-header-size`][] CLI
 option.
 
 This can be overridden for servers and client requests by passing the