wasi: use free() to release preopen array

As this is allocated with `Calloc()`, we cannot use `delete[]` here.

PR-URL: https://github.com/nodejs/node/pull/33110


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: James M Snell <jasnell@gmail.com>