src: remove outdated FIXME in node_crypto.cc

Issue 4641 contains a FIXME regarding the InitCrypto function. After
discussing this with bnoordhuis it seems to be an outdated comment.

Refs: https://github.com/nodejs/node/issues/4641
PR-URL: https://github.com/nodejs/node/pull/11669


Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>