doc: clean up weird notes about reentrancy

All N-API methods are reentrant, it does not make sense to talk
about specific ones here.

Some of these methods can run JS code, which of course can run
other N-API code. For those methods, let’s note that down explicitly.

PR-URL: https://github.com/nodejs/node/pull/40107


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>