doc: fix http properties documented as methods

* at 9772fb92
  [`maxHeadersCount`][maxheaderscount] and [`timeout`][timeout]
  were erroneously changed to methods
* `maxHeadersCount` was also listed to default to `1000` where
  it actually is [`2000`][default]

[maxheaderscount]: https://github.com/nodejs/node/blob/e0a9ad1af244f8756a228a6d087b3a55ee4c0d14/lib/_http_server.js#L276
[timeout]: https://github.com/nodejs/node/blob/e0a9ad1af244f8756a228a6d087b3a55ee4c0d14/lib/_http_server.js#L273
[default]: https://github.com/nodejs/node/blob/e0a9ad1af244f8756a228a6d087b3a55ee4c0d14/lib/_http_server.js#L312

PR-URL: https://github.com/nodejs/node/pull/12039


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>