doc: fix misleading sentence in http.md

Calling `response.end(data)` is not 100% equivalent to calling
`response.write(data)` followed by `response.end()`.

PR-URL: https://github.com/nodejs/node/pull/26465
Fixes: https://github.com/nodejs/node/issues/26005


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>