doc: simplify governance info in README intro

Remove unnecessary wordiness in the governance sentence. It appears very
early in the README so it should be short and clear. This also removes
an instance of passive voice.

PR-URL: https://github.com/nodejs/node/pull/23320


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>