crypto: remove arbitrary UTF16 restriction

Since 71f633a3, this is no longer necessary.

Refs: https://github.com/nodejs/node/pull/22622
Fixes: https://github.com/nodejs/node/issues/29793

PR-URL: https://github.com/nodejs/node/pull/29795


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>