doc: fix up N-API support matrix

The support matrix was out of date. Update
with current status.

Fixes: https://github.com/nodejs/node/issues/25801

PR-URL: https://github.com/nodejs/node/pull/26377


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>